Merge pull request #847 from manongjohn/implicit_holds

Implicit Frame Hold

stuff/config/qss/Dark/Dark.qss

@@ -2283,6 +2283,7 @@ XsheetViewer {
   qproperty-LightBGColor: #d8d8d8;
   qproperty-DarkBGColor: #c9c9c9;
   qproperty-DarkLineColor: #7e7e7e;
+  qproperty-ImplicitCellAlpha: 60;
   qproperty-TimelineIconLineColor: rgba(0, 0, 0, 0.4);
   qproperty-XsheetColumnNameBgColor: rgba(0, 0, 0, 0);
   qproperty-XsheetDragBarHighlightColor: rgba(255, 255, 255, 0.15);

stuff/config/qss/Darker/Darker.qss

@@ -2283,6 +2283,7 @@ XsheetViewer {
   qproperty-LightBGColor: #c8c8c8;
   qproperty-DarkBGColor: #b9b9b9;
   qproperty-DarkLineColor: #6e6e6e;
+  qproperty-ImplicitCellAlpha: 60;
   qproperty-TimelineIconLineColor: rgba(0, 0, 0, 0.3);
   qproperty-XsheetColumnNameBgColor: rgba(0, 0, 0, 0);
   qproperty-XsheetDragBarHighlightColor: rgba(255, 255, 255, 0.15);

stuff/config/qss/Light/Light.qss

@@ -2283,6 +2283,7 @@ XsheetViewer {
   qproperty-LightBGColor: #ffffff;
   qproperty-DarkBGColor: #ffffff;
   qproperty-DarkLineColor: #ffffff;
+  qproperty-ImplicitCellAlpha: 115;
   qproperty-TimelineIconLineColor: rgba(0, 0, 0, 0.144);
   qproperty-XsheetColumnNameBgColor: rgba(0, 0, 0, 0);
   qproperty-XsheetDragBarHighlightColor: rgba(255, 255, 255, 0.15);

stuff/config/qss/Medium/Medium.qss

@@ -2283,6 +2283,7 @@ XsheetViewer {
   qproperty-LightBGColor: #f0f0f0;
   qproperty-DarkBGColor: #e1e1e1;
   qproperty-DarkLineColor: #969696;
+  qproperty-ImplicitCellAlpha: 60;
   qproperty-TimelineIconLineColor: rgba(0, 0, 0, 0.3);
   qproperty-XsheetColumnNameBgColor: rgba(0, 0, 0, 0);
   qproperty-XsheetDragBarHighlightColor: rgba(255, 255, 255, 0.15);

stuff/config/qss/Medium/less/Medium.less

@@ -423,6 +423,8 @@
 @cellHighlightTintColor:                    @hl-bg-color;
 @cellHighlightTintAmount:                   77;
 
+@xsheet-ImplicitCellAlpha:                  60;
+
 @xsheet-EmptyCell-color:                    @xsheet-OnionSkinAreaBG-color;
 @xsheet-NotEmptyColumn-color:               darken(@bg, 3);
 @xsheet-SelectedEmptyCell-color:            fade(mix(lighten(@xsheet-EmptyCell-color, 20), @cellHighlightTintColor, 80), 50);

stuff/config/qss/Medium/less/layouts/xsheet.less

@@ -153,6 +153,8 @@ XsheetViewer {
   qproperty-DarkBGColor: @xsheet-DarkBG-color;
   qproperty-DarkLineColor: @xsheet-DarkLine-color;
 
+  qproperty-ImplicitCellAlpha: @xsheet-ImplicitCellAlpha;
+
   // Column Header: Vertical
   qproperty-TimelineIconLineColor: @timeline-IconLine-color;
   qproperty-XsheetColumnNameBgColor: @xsheet-ColumnNameBg-color;

stuff/config/qss/Medium/less/themes/Light.less

@@ -191,6 +191,8 @@
 @columnBorderDarkness:                      15;
 @cellHighlightLightness:                    10;
 
+@xsheet-ImplicitCellAlpha:                  115;
+
 @xsheet-EmptyCell-color:                    @xsheet-OnionSkinAreaBG-color;
 @xsheet-NotEmptyColumn-color:               @xsheet-bg-color;
 @xsheet-SelectedEmptyCell-color:            fade(mix(lighten(@xsheet-EmptyCell-color, -20), @cellHighlightTintColor, 80), 50);

stuff/config/qss/Medium/less/themes/Neutral.less

@@ -218,6 +218,8 @@
 @columnBorderDesaturation:                  0;
 @columnBorderDarkness:                      15;
 
+@xsheet-ImplicitCellAlpha:                  75;
+
 @xsheet-LevelColumn-color:                  #78a578;
 @xsheet-VectorColumn-color:                 #a7637d;
 @xsheet-ChildColumn-color:                  #9a759c;

stuff/config/qss/Neutral/Neutral.qss

@@ -2283,6 +2283,7 @@ XsheetViewer {
   qproperty-LightBGColor: #ffffff;
   qproperty-DarkBGColor: #ffffff;
   qproperty-DarkLineColor: #cecece;
+  qproperty-ImplicitCellAlpha: 75;
   qproperty-TimelineIconLineColor: rgba(0, 0, 0, 0.3);
   qproperty-XsheetColumnNameBgColor: rgba(0, 0, 0, 0);
   qproperty-XsheetDragBarHighlightColor: rgba(255, 255, 255, 0.15);

stuff/profiles/layouts/settings/quicktoolbar.xml

@@ -3,6 +3,7 @@
     <command>MI_ToggleAutoCreate</command>
     <command>MI_ToggleCreationInHoldCells</command>
     <command>MI_ToggleAutoStretch</command>
+    <command>MI_ToggleImplicitHold</command>
     <separator/>
     <command>MI_NewVectorLevel</command>
     <command>MI_NewToonzRasterLevel</command>

toonz/sources/common/tsystem/tfilepath.cpp

@@ -95,6 +95,8 @@ std::string TFrameId::expand(FrameFormat format) const {
     return "";
   else if (m_frame == NO_FRAME)
     return "-";
+  else if (m_frame == STOP_FRAME)
+    return "x";
   std::ostringstream o_buff;
   if (format == FOUR_ZEROS || format == UNDERSCORE_FOUR_ZEROS) {
     o_buff.fill('0');

toonz/sources/include/tfilepath.h

@@ -36,7 +36,8 @@ class DVAPI TFrameId {
 public:
   enum {
     EMPTY_FRAME = -1,  // es. pippo..tif
-    NO_FRAME    = -2   // es. pippo.tif
+    NO_FRAME    = -2,  // es. pippo.tif
+    STOP_FRAME  = -3
   };
 
   enum FrameFormat {
@@ -86,6 +87,7 @@ public:
 
   bool isEmptyFrame() const { return m_frame == EMPTY_FRAME; }
   bool isNoFrame() const { return m_frame == NO_FRAME; }
+  bool isStopFrame() const { return m_frame == STOP_FRAME; }
 
   // operator string() const;
   std::string expand(FrameFormat format = FOUR_ZEROS) const;
@@ -280,6 +282,9 @@ type is a string that indicate the filename extension(ex:. bmp or .bmp)*/
   TFilePath withNoFrame() const {
     return withFrame(TFrameId(TFrameId::NO_FRAME));
   }  // pippo.tif
+  TFilePath withStopFrame() const {
+    return withFrame(TFrameId(TFrameId::STOP_FRAME));
+  }
 
   TFilePath operator+(const TFilePath &fp) const;
   TFilePath &operator+=(const TFilePath &fp) /*{*this=*this+fp;return *this;}*/;

toonz/sources/include/toonz/preferences.h

@@ -304,6 +304,9 @@ public:
   bool isAutoCreateEnabled() const { return getBoolValue(EnableAutocreation); }
   int getNumberingSystem() const { return getIntValue(NumberingSystem); }
   bool isAutoStretchEnabled() const { return getBoolValue(EnableAutoStretch); }
+  bool isImplicitHoldEnabled() const {
+    return getBoolValue(EnableImplicitHold);
+  }
   bool isCreationInHoldCellsEnabled() const {
     return getBoolValue(EnableCreationInHoldCells);
   }

toonz/sources/include/toonz/preferencesitemids.h

@@ -90,6 +90,7 @@ enum PreferencesItemId {
   EnableAutocreation,
   NumberingSystem,
   EnableAutoStretch,
+  EnableImplicitHold,
   EnableCreationInHoldCells,
   EnableAutoRenumber,
   vectorSnappingTarget,

toonz/sources/include/toonz/txshcolumn.h

@@ -141,7 +141,7 @@ Constructs a TXshColumn with default value.
   virtual TXshZeraryFxColumn *getZeraryFxColumn() { return 0; }
   virtual TXshMeshColumn *getMeshColumn() { return 0; }
 
-  virtual int getMaxFrame() const = 0;
+  virtual int getMaxFrame(bool ignoreLastStop = false) const = 0;
 
   virtual TXshColumn *clone() const = 0;
 
@@ -219,7 +219,7 @@ If r0=r1=row return false.
 */
   virtual bool getLevelRange(int row, int &r0, int &r1) const = 0;
 
-  virtual int getRange(int &r0, int &r1) const {
+  virtual int getRange(int &r0, int &r1, bool ignoreLastStop = false) const {
     r0 = 0;
     r1 = -1;
     return 0;
@@ -330,7 +330,7 @@ Return not empty cell range. Set \b r0 and \b r1 to first
 and last row with not empty cell.
 \sa isEmpty() and getRowCount()
 */
-  int getRange(int &r0, int &r1) const override;
+  int getRange(int &r0, int &r1, bool ignoreLastStop = false) const override;
   /*!
 Return row count.
 \sa isEmpty() and getRange()
@@ -386,7 +386,7 @@ Clear \b rowCount cells from line \b row, without shift.
   /*!
 Return last row with not empty cell.
 */
-  int getMaxFrame() const override;
+  int getMaxFrame(bool ignoreLastStop = false) const override;
 
   /*!
 Return first not empty row.

toonz/sources/include/toonz/txsheet.h

@@ -196,6 +196,10 @@ public:
 
   const TXshCell &getCell(const CellPosition &pos) const;
 
+  bool isImplicitCell(int row, int col) const;
+
+  bool isImplicitCell(const CellPosition &pos) const;
+
   bool setCell(int row, int col, const TXshCell &cell);
   /*! Set \b \e cells[] to \b \e rowCount cells of column identified by index \b
      \e col starting from row identified by index \b \e row. If column is empty

toonz/sources/include/toonz/txshsoundcolumn.h

@@ -129,11 +129,11 @@ public:
   void saveData(TOStream &os) override;
 
   /*! r0 : min row not empty, r1 : max row not empty. Return row count.*/
-  int getRange(int &r0, int &r1) const override;
+  int getRange(int &r0, int &r1, bool ignoreLastStop = false) const override;
   /*! Last not empty row - first not empty row. */
   int getRowCount() const override;
   /*! Return max row not empty. */
-  int getMaxFrame() const override;
+  int getMaxFrame(bool ignoreLastStop = false) const override;
   /*! Return min row not empty.*/
   int getFirstRow() const override;
 

toonz/sources/stdfx/externalpalettefx.cpp

@@ -61,6 +61,17 @@ TPalette *getPalette(TXshColumn *column, int frame) {
   if (!cellColumn) return 0;
 
   TXshCell cell = cellColumn->getCell(frame);
+  // This is only relevant when Implicit Holds are enabled
+  if (cell.isEmpty()) {
+    int r0, r1;
+    cellColumn->getRange(r0, r1);
+    for (int r = std::min(r1, frame); r >= r0; r--) {
+      cell = cellColumn->getCell(r);
+      if (cell.isEmpty()) continue;
+      break;
+    }
+  }
+
   if (cell.isEmpty()) return 0;
 
   TXshPaletteLevel *pl = cell.m_level->getPaletteLevel();

toonz/sources/tnztools/tool.cpp

@@ -353,6 +353,11 @@ TImage *TTool::touchImage() {
   if (!xsh) return 0;
 
   TXshCell cell       = xsh->getCell(row, col);
+  bool isImplicitCell = xsh->isImplicitCell(row, col);
+
+  // Stop frames cannot be modified
+  if (cell.getFrameId().isStopFrame()) return 0;
+
   TXshSimpleLevel *sl = cell.getSimpleLevel();
 
   if (sl) {
@@ -380,7 +385,9 @@ TImage *TTool::touchImage() {
       // measure the hold length (starting from the current row) : r0-r1
       int r0 = row, r1 = row;
       if (isAutoStretchEnabled)
-        while (xsh->getCell(r1 + 1, col) == cell) r1++;
+        while (xsh->getCell(r1 + 1, col) == cell &&
+               !xsh->isImplicitCell(r1 + 1, col))
+          r1++;
       // find the proper frameid (possibly addisng suffix, in order to avoid a
       // fid already used)
       // find the proper frameid
@@ -418,7 +425,10 @@ TImage *TTool::touchImage() {
       currentXsheet->notifyXsheetChanged();
       currentScene->notifyCastChange();
       currentLevel->notifyLevelChange();
-      m_cellsData.push_back({r0, r1, CellOps::ExistingToNew});
+      if (isImplicitCell)
+        m_cellsData.push_back({r0, r1, CellOps::BlankToNew});
+      else
+        m_cellsData.push_back({r0, r1, CellOps::ExistingToNew});
     }
     // if the level does not contain a frame in the current cell
     // (i.e. drawing on the cell with red numbers)
@@ -728,7 +738,8 @@ TFrameId TTool::getCurrentFid() const {
   int col = m_application->getCurrentColumn()->getColumnIndex();
   TXshCell cell =
       m_application->getCurrentXsheet()->getXsheet()->getCell(row, col);
-  if (cell.isEmpty()) return TFrameId::NO_FRAME;
+  if (cell.isEmpty() || cell.getFrameId().isStopFrame())
+    return TFrameId::NO_FRAME;
 
   return cell.getFrameId();
 }
@@ -1108,6 +1119,13 @@ QString TTool::updateEnabled(int rowIndex, int columnIndex) {
                                 "frames of a Single Frame level."));
         }
       }
+ 
+      // Stop frames cannot be modified
+      if (xsh->getCell(rowIndex, columnIndex).getFrameId().isStopFrame()) {
+        return (
+            enable(false),
+            QObject::tr("The current tool cannot be used on a stop frame."));
+      }
     }
   }
 

toonz/sources/toonz/autoinputcellnumberpopup.cpp

@@ -149,12 +149,25 @@ AutoInputCellNumberUndo::AutoInputCellNumberUndo(int increment, int interval,
         (m_r1 == -1) ? m_rowsCount - 1 : std::min(m_r1, m_r0 + m_rowsCount - 1);
     m_beforeCells.reset(
         new TXshCell[m_columnIndices.size() * (rowUpTo - m_r0 + 1)]);
-    int k = 0;
+    int k        = 0;
+    TXsheetP xsh = TApp::instance()->getCurrentXsheet()->getXsheet();
     for (int c = 0; c < m_columnIndices.size(); ++c) {
-      for (int r = m_r0; r <= rowUpTo; ++r)
+      for (int r = m_r0; r <= rowUpTo; ++r) {
+        const TXshCell &cell = xsh->getCell(r, m_columnIndices.at(c));
         m_beforeCells[k++] =
-            TApp::instance()->getCurrentXsheet()->getXsheet()->getCell(
-                r, m_columnIndices.at(c));
+            xsh->isImplicitCell(r, m_columnIndices.at(c)) ? TXshCell() : cell;
+      }
+    }
+  } else {
+    // Need to restore rows starting with implicit cells that were converted to
+    // actual cells by this process
+    m_beforeCells.reset(new TXshCell[m_columnIndices.size()]);
+    int k        = 0;
+    TXsheetP xsh = TApp::instance()->getCurrentXsheet()->getXsheet();
+    for (int c = 0; c < m_columnIndices.size(); ++c) {
+      const TXshCell &cell = xsh->getCell(m_r0, m_columnIndices.at(c));
+      m_beforeCells[k++] =
+          xsh->isImplicitCell(m_r0, m_columnIndices.at(c)) ? TXshCell() : cell;
     }
   }
 }
@@ -178,6 +191,15 @@ void AutoInputCellNumberUndo::undo() const {
   } else {  // on insert case, remove inserted cells
     for (int c = 0; c < m_columnIndices.size(); ++c)
       xsh->removeCells(m_r0, m_columnIndices.at(c), m_rowsCount);
+
+    int k = 0;
+    for (int c = 0; c < m_columnIndices.size(); ++c) {
+      if (m_beforeCells[k].isEmpty())
+        xsh->clearCells(m_r0, m_columnIndices.at(c));
+      else
+        xsh->setCell(m_r0, m_columnIndices.at(c), m_beforeCells[k]);
+      k++;
+    }
   }
   TApp::instance()->getCurrentXsheet()->notifyXsheetChanged();
 }

toonz/sources/toonz/celldata.cpp

@@ -11,6 +11,7 @@
 #include "toonz/tcolumnfx.h"
 #include "toonz/fxdag.h"
 #include "toonz/txshlevelcolumn.h"
+#include "toonz/preferences.h"
 
 //-----------------------------------------------------------------------------
 
@@ -194,7 +195,12 @@ void TCellData::cloneZeraryFx(int index, std::vector<TXshCell> &cells) const {
     newFxLevel->setColumn(newFxColumn);
     // replace the zerary fx cells by the new fx
     int r;
-    for (r     = firstNotEmptyIndex; r < (index + 1) * m_rowCount; r++)
-      cells[r] = TXshCell(newFxLevel, m_cells[r].getFrameId());
+    for (r = firstNotEmptyIndex; r < (index + 1) * m_rowCount; r++) {
+      if (Preferences::instance()->isImplicitHoldEnabled() &&
+          m_cells[r].getFrameId().isEmptyFrame())
+        cells[r] = TXshCell(0, m_cells[r].getFrameId());
+      else
+        cells[r] = TXshCell(newFxLevel, m_cells[r].getFrameId());
+    }
   }
 }

toonz/sources/toonz/cellselection.cpp

@@ -53,6 +53,8 @@
 #include "toonz/levelset.h"
 #include "toonz/tstageobjecttree.h"
 #include "toonz/stage.h"
+#include "toonz/txshzeraryfxlevel.h"
+#include "toonz/txshpalettelevel.h"
 #include "vectorizerpopup.h"
 #include "tools/rasterselection.h"
 #include "tools/strokeselection.h"
@@ -1264,6 +1266,47 @@ public:
 
 //-----------------------------------------------------------------------------
 
+class StopFrameHoldUndo final : public TUndo {
+  TXshLevel *m_level;
+  TXshCell m_oldCell;
+  int m_row;
+  int m_col;
+
+public:
+  StopFrameHoldUndo(TXshLevel *level, int row, int col, TXshCell oldCell)
+      : m_level(level), m_row(row), m_col(col), m_oldCell(oldCell) {}
+
+  ~StopFrameHoldUndo() {}
+
+  void undo() const override {
+    TXsheet *xsh = TApp::instance()->getCurrentXsheet()->getXsheet();
+
+    xsh->clearCells(m_row, m_col, 1);
+    xsh->setCell(m_row, m_col, m_oldCell);
+
+    TApp::instance()->getCurrentXsheet()->notifyXsheetChanged();
+  }
+
+  void redo() const override {
+    TXsheet *xsh = TApp::instance()->getCurrentXsheet()->getXsheet();
+
+    xsh->setCell(m_row, m_col, TXshCell(m_level, TFrameId::STOP_FRAME));
+
+    TApp::instance()->getCurrentXsheet()->notifyXsheetChanged();
+  }
+
+  int getSize() const override { return sizeof(*this); }
+
+  QString getHistoryString() override {
+    return QObject::tr("Set Stop Frame Hold");
+  }
+
+  int getHistoryType() override { return HistoryType::Xsheet; }
+  //-----------------------------------------------------------------------------
+};
+
+//-----------------------------------------------------------------------------
+
 class DuplicateDrawingUndo final : public ToolUtils::TToolUndo {
   TFrameId origFrameId;
   TFrameId dupFrameId;
@@ -1511,6 +1554,7 @@ void TCellSelection::enableCommands() {
                 &TCellSelection::createBlankDrawings);
   enableCommand(this, MI_Duplicate, &TCellSelection::duplicateFrames);
   enableCommand(this, MI_PasteDuplicate, &TCellSelection::pasteDuplicateCells);
+  enableCommand(this, MI_StopFrameHold, &TCellSelection::stopFrameHold);
 }
 //-----------------------------------------------------------------------------
 // Used in RenameCellField::eventFilter()
@@ -1555,7 +1599,8 @@ bool TCellSelection::isEnabledCommand(
                                         MI_ConvertToToonzRaster,
                                         MI_ConvertVectorToVector,
                                         MI_CreateBlankDrawing,
-                                        MI_FillEmptyCell};
+                                        MI_FillEmptyCell,
+                                        MI_StopFrameHold};
   return commands.contains(commandId);
 }
 
@@ -2714,8 +2759,9 @@ void TCellSelection::createBlankDrawing(int row, int col, bool multiple) {
 
   TXshCell cell       = xsh->getCell(row, col);
   TXshSimpleLevel *sl = cell.getSimpleLevel();
+  bool isStopFrame = cell.getFrameId().isStopFrame();
 
-  if (!img || !sl) {
+  if ((!img || !sl) && !isStopFrame) {
     //----- Restore previous states of autocreation
     if (!isAutoCreateEnabled)
       Preferences::instance()->setValue(EnableAutocreation, false, false);
@@ -2738,8 +2784,12 @@ void TCellSelection::createBlankDrawing(int row, int col, bool multiple) {
                                         false);
     //------------------
     if (!multiple)
-      DVGui::warning(QObject::tr(
-          "Unable to replace the current drawing with a blank drawing"));
+      if (isStopFrame)
+        DVGui::warning(QObject::tr(
+            "Unable to replace a Stop Frame Hold with a blank drawing"));
+      else
+        DVGui::warning(QObject::tr(
+            "Unable to replace the current drawing with a blank drawing"));
     return;
   }
 
@@ -2787,6 +2837,98 @@ void TCellSelection::createBlankDrawings() {
 
 //-----------------------------------------------------------------------------
 
+void TCellSelection::stopFrameHold(int row, int col, bool multiple) {
+  TXsheet *xsh = TApp::instance()->getCurrentXsheet()->getXsheet();
+
+  if (col < 0) {
+    if (!multiple)
+      DVGui::warning(QObject::tr(
+          "Unable to create a stop frame hold on the camera column"));
+    return;
+  }
+
+  TXshColumn *column = xsh->getColumn(col);
+  if (column && column->isLocked()) {
+    if (!multiple) DVGui::warning(QObject::tr("The current column is locked"));
+    return;
+  }
+
+  TApp::instance()->getCurrentColumn()->setColumnIndex(col);
+  TApp::instance()->getCurrentFrame()->setCurrentFrame(row + 1);
+
+  TXshLevel *level = TApp::instance()->getCurrentLevel()->getLevel();
+  if (!level) {
+    int r0, r1;
+    xsh->getCellRange(col, r0, r1);
+    for (int r = std::min(r1, row); r >= r0; r--) {
+      TXshCell cell = xsh->getCell(r, col);
+      if (cell.isEmpty()) continue;
+      level = cell.m_level.getPointer();
+      if (!level) continue;
+      break;
+    }
+  }
+  if (level) {
+    int levelType = level->getType();
+    if (levelType == SND_XSHLEVEL || levelType == SND_TXT_XSHLEVEL) {
+      if (!multiple)
+        DVGui::warning(QObject::tr(
+            "Cannot create a stop frame hold on the current column"));
+      return;
+    }
+  } else {
+    if (!multiple)
+      DVGui::warning(QObject::tr(
+          "Cannot create a stop from hold on a column without a level"));
+    return;
+  }
+
+  TXshLevel *lvl = level->getSimpleLevel();
+  if (!lvl) lvl  = level->getChildLevel();
+  if (!lvl) lvl  = dynamic_cast<TXshLevel *>(level->getPaletteLevel());
+  if (!lvl) lvl  = dynamic_cast<TXshLevel *>(level->getZeraryFxLevel());
+
+  if (!lvl) {
+    if (!multiple)
+      DVGui::warning(QObject::tr(
+          "Unable to create a stop frame hold on the current column"));
+    return;
+  }
+
+  TXshCell cell;
+  if (!xsh->isImplicitCell(row, col)) cell = xsh->getCell(row, col);
+
+  StopFrameHoldUndo *undo = new StopFrameHoldUndo(lvl, row, col, cell);
+  TUndoManager::manager()->add(undo);
+
+  undo->redo();
+}
+
+//-----------------------------------------------------------------------------
+
+void TCellSelection::stopFrameHold() {
+  int col = TApp::instance()->getCurrentColumn()->getColumnIndex();
+  int row = TApp::instance()->getCurrentFrame()->getFrameIndex();
+
+  int r0, c0, r1, c1;
+  getSelectedCells(r0, c0, r1, c1);
+
+  bool multiple = (r1 - r0 > 1) || (c1 - c0 > 1);
+
+  TUndoManager::manager()->beginBlock();
+  for (int c = c0; c <= c1; c++) {
+    for (int r = r0; r <= r1; r++) {
+      stopFrameHold(r, c, multiple);
+    }
+  }
+  TUndoManager::manager()->endBlock();
+
+  TApp::instance()->getCurrentColumn()->setColumnIndex(col);
+  TApp::instance()->getCurrentFrame()->setCurrentFrame(row + 1);
+}
+
+//-----------------------------------------------------------------------------
+
 void TCellSelection::duplicateFrame(int row, int col, bool multiple) {
   TXsheet *xsh = TApp::instance()->getCurrentXsheet()->getXsheet();
 
@@ -2811,7 +2953,7 @@ void TCellSelection::duplicateFrame(int row, int col, bool multiple) {
       Preferences::instance()->isAnimationSheetEnabled()) {
     int r0, r1;
     xsh->getCellRange(col, r0, r1);
-    for (int r = std::min(r1, row); r > r0; r--) {
+    for (int r = std::min(r1, row); r >= r0; r--) {
       TXshCell cell = xsh->getCell(r, col);
       if (cell.isEmpty()) continue;
       level = cell.m_level.getPointer();
@@ -2838,7 +2980,6 @@ void TCellSelection::duplicateFrame(int row, int col, bool multiple) {
 
   TXshCell targetCell = xsh->getCell(row, col);
   TXshCell prevCell   = xsh->getCell(row - 1, col);
-  ;
 
   // check if we use the current cell to duplicate or the previous cell
   if (!targetCell.isEmpty() && targetCell != prevCell) {
@@ -2849,6 +2990,12 @@ void TCellSelection::duplicateFrame(int row, int col, bool multiple) {
     row++;
   }
 
+  if (prevCell.getFrameId().isStopFrame()) {
+    if (!xsh->isImplicitCell(row - 1, col) && !multiple)
+      DVGui::warning(QObject::tr("Cannot duplicate a Stop Frame Hold"));
+    return;
+  }
+
   if (prevCell.isEmpty() || !(prevCell.m_level->getSimpleLevel())) return;
 
   TXshSimpleLevel *sl = prevCell.getSimpleLevel();

toonz/sources/toonz/cellselection.h

@@ -125,6 +125,8 @@ public:
 
   void createBlankDrawing(int row, int col, bool inRange);
   void createBlankDrawings();
+  void stopFrameHold(int row, int col, bool inRange);
+  void stopFrameHold();
   void fillEmptyCell();
 };
 

toonz/sources/toonz/cellselectioncommand.cpp

@@ -209,7 +209,7 @@ void IncrementUndo::undo() const {
     const TRect &r = m_undoCells[i].first;
     int size       = r.x1 - r.x0 + 1;
 
-    if (m_undoCells[i].second.isEmpty())
+    if (m_undoCells[i].second.getFrameId().isNoFrame())
       xsh->removeCells(r.x0, r.y0, size);
     else {
       xsh->insertCells(r.x0, r.y0, size);
@@ -387,11 +387,13 @@ StepUndo::StepUndo(int r0, int c0, int r1, int c1, int step)
   assert(m_rowsCount > 0 && m_colsCount > 0 && step > 0);
   assert(m_cells);
 
-  int k = 0;
+  TXsheetP xsh = TApp::instance()->getCurrentXsheet()->getXsheet();
+  int k        = 0;
   for (int r = r0; r <= r1; ++r)
-    for (int c = c0; c <= c1; ++c)
-      m_cells[k++] =
-          TApp::instance()->getCurrentXsheet()->getXsheet()->getCell(r, c);
+    for (int c = c0; c <= c1; ++c) {
+      const TXshCell &cell = xsh->getCell(r, c);
+      m_cells[k++] = xsh->isImplicitCell(r, c) ? TXshCell() : cell;
+    }
 }
 
 //-----------------------------------------------------------------------------
@@ -489,11 +491,13 @@ EachUndo::EachUndo(int r0, int c0, int r1, int c1, int each)
   assert(m_rowsCount > 0 && m_colsCount > 0 && each > 0);
   assert(m_cells);
 
-  int k = 0;
+  int k        = 0;
+  TXsheetP xsh = TApp::instance()->getCurrentXsheet()->getXsheet();
   for (int r = r0; r <= r1; ++r)
-    for (int c = c0; c <= c1; ++c)
-      m_cells[k++] =
-          TApp::instance()->getCurrentXsheet()->getXsheet()->getCell(r, c);
+    for (int c = c0; c <= c1; ++c) {
+      const TXshCell &cell = xsh->getCell(r, c);
+      m_cells[k++] = xsh->isImplicitCell(r, c) ? TXshCell() : cell;
+    }
 }
 
 //-----------------------------------------------------------------------------
@@ -598,13 +602,16 @@ ReframeUndo::ReframeUndo(int r0, int r1, std::vector<int> columnIndeces,
     , m_withBlank(withBlank) {
   m_nr = m_r1 - m_r0 + 1;
   assert(m_nr > 0);
-  m_cells.reset(new TXshCell[m_nr * (int)m_columnIndeces.size()]);
+  m_cells.reset(new TXshCell[(m_nr + 1) * (int)m_columnIndeces.size()]);
   assert(m_cells);
-  int k = 0;
-  for (int r = r0; r <= r1; r++)
-    for (int c     = 0; c < (int)m_columnIndeces.size(); c++)
-      m_cells[k++] = TApp::instance()->getCurrentXsheet()->getXsheet()->getCell(
-          r, m_columnIndeces[c]);
+  int k        = 0;
+  TXsheet *xsh = TApp::instance()->getCurrentXsheet()->getXsheet();
+  for (int r = r0; r <= (r1 + 1); r++)
+    for (int c = 0; c < (int)m_columnIndeces.size(); c++) {
+      const TXshCell &cell = xsh->getCell(r, m_columnIndeces[c]);
+      m_cells[k++] =
+          xsh->isImplicitCell(r, m_columnIndeces[c]) ? TXshCell() : cell;
+    }
 
   m_newRows.clear();
 }
@@ -633,7 +640,7 @@ void ReframeUndo::undo() const {
 
   if (m_cells) {
     int k = 0;
-    for (int r = m_r0; r <= m_r1; r++)
+    for (int r = m_r0; r <= m_r1 + 1; r++)
       for (int c = 0; c < m_columnIndeces.size(); c++) {
         if (m_cells[k].isEmpty())
           xsh->clearCells(r, m_columnIndeces[c]);
@@ -834,10 +841,10 @@ ResetStepUndo::ResetStepUndo(int r0, int c0, int r1, int c1)
     TXshCell prevCell;
     m_insertedCells[c] = 0;
 
+    TXsheetP xsh = app->getCurrentXsheet()->getXsheet();
     for (int r = r0; r <= r1; ++r) {
-      const TXshCell &cell =
-          app->getCurrentXsheet()->getXsheet()->getCell(r, c);
-      m_cells[k++] = cell;
+      const TXshCell &cell = xsh->getCell(r, c);
+      m_cells[k++] = xsh->isImplicitCell(r, c) ? TXshCell() : cell;
 
       if (prevCell != cell) {
         prevCell = cell;
@@ -934,10 +941,10 @@ IncreaseStepUndo::IncreaseStepUndo(int r0, int c0, int r1, int c1)
     TXshCell prevCell;
     m_insertedCells[c] = 0;
 
+    TXsheetP xsh = TApp::instance()->getCurrentXsheet()->getXsheet();
     for (int r = r0; r <= r1; ++r) {
-      const TXshCell &cell =
-          TApp::instance()->getCurrentXsheet()->getXsheet()->getCell(r, c);
-      m_cells[k++] = cell;
+      const TXshCell &cell = xsh->getCell(r, c);
+      m_cells[k++] = xsh->isImplicitCell(r, c) ? TXshCell() : cell;
 
       if (prevCell != cell) {
         prevCell = cell;
@@ -1045,19 +1052,18 @@ DecreaseStepUndo::DecreaseStepUndo(int r0, int c0, int r1, int c1)
     , m_newR1(m_r1) {
   assert(m_cells);
 
-  int k = 0;
+  int k        = 0;
+  TXsheetP xsh = TApp::instance()->getCurrentXsheet()->getXsheet();
   for (int c = c0; c <= c1; ++c) {
-    TXshCell prevCell =
-        TApp::instance()->getCurrentXsheet()->getXsheet()->getCell(r0, c);
+    TXshCell prevCell = xsh->getCell(r0, c);
     m_removedCells[c] = 0;
 
     bool removed = false;
-    m_cells[k++] = prevCell;
+    m_cells[k++] = xsh->isImplicitCell(r0, c) ? TXshCell() : prevCell;
 
     for (int r = r0 + 1; r <= r1; ++r) {
-      const TXshCell &cell =
-          TApp::instance()->getCurrentXsheet()->getXsheet()->getCell(r, c);
-      m_cells[k++] = cell;
+      const TXshCell &cell = xsh->getCell(r, c);
+      m_cells[k++] = xsh->isImplicitCell(r, c) ? TXshCell() : cell;
 
       if (prevCell == cell) {
         if (!removed) {
@@ -1120,7 +1126,8 @@ void TCellSelection::decreaseStepCells() {
     for (int i = 1; sameCells; i++) {
       nextCell = xsh->getCell(row + i, col);
       if (nextCell.m_frameId == cell.m_frameId &&
-          nextCell.m_level == cell.m_level) {
+          nextCell.m_level == cell.m_level &&
+          !xsh->isImplicitCell(row + i, col)) {
         r1 = row + i;
       } else
         sameCells = false;
@@ -1595,20 +1602,35 @@ void CloneLevelUndo::insertCells() const {
     m_insertedColumns.insert(colIndex);
   }
 
+  bool useImplicitHold = Preferences::instance()->isImplicitHoldEnabled();
+
   // Now, re-traverse the selected range, and add corresponding cells
   // in the destination range
   for (int c = m_range.m_c0; c <= m_range.m_c1; ++c) {
+    TXshCell prevCell;
+    TXshLevelP lastLevel = 0;
     for (int r = m_range.m_r0; r <= m_range.m_r1; ++r) {
-      const TXshCell &srcCell = xsh->getCell(r, c);
+      TXshCell srcCell = xsh->getCell(r, c);
+      if (useImplicitHold) {
+        if (r > m_range.m_r0 &&
+            (prevCell == srcCell || xsh->isImplicitCell(r, c)))
+          srcCell = TXshCell();
+        prevCell = srcCell;
+      }
       if (TXshSimpleLevel *srcSl = srcCell.getSimpleLevel()) {
         std::map<TXshSimpleLevel *, TXshLevelP>::iterator lt =
             m_insertedLevels.find(srcSl);
         if (lt != m_insertedLevels.end()) {
+          lastLevel = lt->second;
           TXshCell dstCell(lt->second, srcCell.getFrameId());
           xsh->setCell(r, c + m_range.getColCount(), dstCell);
         }
       }
     }
+    if (useImplicitHold &&
+        !xsh->getCell(m_range.m_r1, c + m_range.getColCount()).isEmpty())
+      xsh->setCell(m_range.m_r1 + 1, c + m_range.getColCount(),
+                   TXshCell(lastLevel, TFrameId::STOP_FRAME));
   }
 }
 

toonz/sources/toonz/icons/dark/actions/16/implicit_hold.svg

@@ -0,0 +1,79 @@
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+<svg
+   xmlns:dc="http://purl.org/dc/elements/1.1/"
+   xmlns:cc="http://creativecommons.org/ns#"
+   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+   xmlns:svg="http://www.w3.org/2000/svg"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   width="16px"
+   height="16px"
+   version="1.1"
+   xml:space="preserve"
+   style="fill-rule:evenodd;clip-rule:evenodd;stroke-linejoin:round;stroke-miterlimit:2;"
+   id="svg20"
+   sodipodi:docname="implicit_hold.svg"
+   inkscape:version="0.92.4 (5da689c313, 2019-01-14)"><metadata
+   id="metadata26"><rdf:RDF><cc:Work
+       rdf:about=""><dc:format>image/svg+xml</dc:format><dc:type
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+   id="defs24" /><sodipodi:namedview
+   pagecolor="#ffffff"
+   bordercolor="#666666"
+   borderopacity="1"
+   objecttolerance="10"
+   gridtolerance="10"
+   guidetolerance="10"
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+   inkscape:pageshadow="2"
+   inkscape:window-width="1920"
+   inkscape:window-height="1013"
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+   inkscape:zoom="51.250051"
+   inkscape:cx="8.0000125"
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+   inkscape:window-x="-9"
+   inkscape:window-y="-9"
+   inkscape:window-maximized="1"
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+    <g
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+            
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+    </g>
+</svg>

toonz/sources/toonz/icons/dark/actions/16/implicit_hold_on.svg

@@ -0,0 +1,75 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<svg
+   xmlns:dc="http://purl.org/dc/elements/1.1/"
+   xmlns:cc="http://creativecommons.org/ns#"
+   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+   xmlns:svg="http://www.w3.org/2000/svg"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   width="16px"
+   height="16px"
+   version="1.1"
+   xml:space="preserve"
+   style="fill-rule:evenodd;clip-rule:evenodd;stroke-linejoin:round;stroke-miterlimit:2;"
+   id="svg20"
+   sodipodi:docname="implicit_hold_on.svg"
+   inkscape:version="0.92.4 (5da689c313, 2019-01-14)"><metadata
+   id="metadata26"><rdf:RDF><cc:Work
+       rdf:about=""><dc:format>image/svg+xml</dc:format><dc:type
+         rdf:resource="http://purl.org/dc/dcmitype/StillImage" /></cc:Work></rdf:RDF></metadata><defs
+   id="defs24"><pattern
+     y="0"
+     x="0"
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+     patternUnits="userSpaceOnUse"
+     id="EMFhbasepattern" /></defs><sodipodi:namedview
+   pagecolor="#ffffff"
+   bordercolor="#666666"
+   borderopacity="1"
+   objecttolerance="10"
+   gridtolerance="10"
+   guidetolerance="10"
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+   inkscape:pageshadow="2"
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+   showgrid="true"
+   inkscape:zoom="51.25"
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+   inkscape:cy="8"
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+   id="bg-1"><rect
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+     style="fill:#878787;fill-opacity:0"
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+       d="M 143.025,25 C 144.116,25 145,24.116 145,23.025 V 12.984 c 0,-0.527 -0.209,-1.031 -0.581,-1.403 C 144.047,11.209 143.543,11 143.016,11 h -10.032 c -0.527,0 -1.031,0.209 -1.403,0.581 -0.372,0.372 -0.581,0.876 -0.581,1.403 v 10.032 c 0,0.527 0.209,1.031 0.581,1.403 0.372,0.372 0.876,0.581 1.403,0.581 z m 0.014,-1 C 143.57,24 144,23.57 144,23.039 V 13.017 c 0,-0.269 -0.107,-0.528 -0.298,-0.719 C 143.511,12.107 143.252,12 142.983,12 h -9.966 c -0.269,0 -0.528,0.107 -0.719,0.298 -0.191,0.191 -0.298,0.45 -0.298,0.719 v 9.966 c 0,0.269 0.107,0.528 0.298,0.719 0.191,0.191 0.45,0.298 0.719,0.298 z m -6.83211,-11.319507 -3.41581,10e-7 v 1.75993 l 3.41965,-2e-6 z m 2.78822,0 h -2.01706 l -0.0135,1.759929 2.02473,0 z m 4.19839,10e-7 -3.4197,-10e-7 -0.006,1.759929 3.41008,2e-6 z"
+       id="path5-1-8" /></g></g></svg>

toonz/sources/toonz/icons/dark/actions/16/stop_frame_hold.svg

@@ -0,0 +1,80 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<svg
+   xmlns:dc="http://purl.org/dc/elements/1.1/"
+   xmlns:cc="http://creativecommons.org/ns#"
+   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+   xmlns:svg="http://www.w3.org/2000/svg"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   width="16px"
+   height="16px"
+   version="1.1"
+   xml:space="preserve"
+   style="fill-rule:evenodd;clip-rule:evenodd;stroke-linejoin:round;stroke-miterlimit:2;"
+   id="svg12"
+   sodipodi:docname="stop_frame_hold.svg"
+   inkscape:version="0.92.4 (5da689c313, 2019-01-14)"><metadata
+   id="metadata18"><rdf:RDF><cc:Work
+       rdf:about=""><dc:format>image/svg+xml</dc:format><dc:type
+         rdf:resource="http://purl.org/dc/dcmitype/StillImage" /></cc:Work></rdf:RDF></metadata><defs
+   id="defs16">
+        
+    </defs><sodipodi:namedview
+   pagecolor="#ffffff"
+   bordercolor="#666666"
+   borderopacity="1"
+   objecttolerance="10"
+   gridtolerance="10"
+   guidetolerance="10"
+   inkscape:pageopacity="0"
+   inkscape:pageshadow="2"
+   inkscape:window-width="1672"
+   inkscape:window-height="865"
+   id="namedview14"
+   showgrid="true"
+   inkscape:zoom="41.7193"
+   inkscape:cx="11.121506"
+   inkscape:cy="7.0977181"
+   inkscape:window-x="0"
+   inkscape:window-y="0"
+   inkscape:window-maximized="0"
+   inkscape:current-layer="svg12"
+   inkscape:snap-grids="true"><inkscape:grid
+     type="xygrid"
+     id="grid827" /></sodipodi:namedview>
+    <g
+   transform="matrix(-1,0,0,1,126,-10)"
+   id="add_cell">
+            <g
+   transform="matrix(0.110345,0,0,0.121212,93.7793,-8.90909)"
+   id="bg">
+                <rect
+   id="rect2"
+   style="fill:#878787;fill-opacity:0"
+   height="132"
+   width="145"
+   y="156"
+   x="147" />
+            </g>
+            <g
+   id="g7"
+   transform="matrix(-1,0,0,1,256,0)">
+                <path
+   inkscape:connector-curvature="0"
+   id="path5"
+   d="m 145,21 v -8.016 c 0,-0.527 -0.209,-1.031 -0.581,-1.403 C 144.047,11.209 143.543,11 143.016,11 h -10.032 c -0.527,0 -1.031,0.209 -1.403,0.581 -0.372,0.372 -0.581,0.876 -0.581,1.403 v 10.032 c 0,0.527 0.209,1.031 0.581,1.403 0.372,0.372 0.876,0.581 1.403,0.581 H 141 c 0.265,0 0.52,-0.105 0.707,-0.293 l 3,-3 C 144.895,21.52 145,21.265 145,21 Z m -1,-1 v -6.983 c 0,-0.27 -0.107,-0.528 -0.298,-0.719 C 143.511,12.107 143.252,12 142.983,12 h -9.966 c -0.269,0 -0.528,0.107 -0.719,0.298 -0.191,0.191 -0.298,0.45 -0.298,0.719 v 9.966 c 0,0.269 0.107,0.528 0.298,0.719 0.191,0.191 0.449,0.298 0.719,0.298 H 140 v -4 z m -3,1 v 3 l 3,-3 z m -5,-7.5 c 0,-0.133 -0.053,-0.26 -0.146,-0.354 C 135.76,13.053 135.633,13 135.5,13 h -2 c -0.133,0 -0.26,0.053 -0.354,0.146 C 133.053,13.24 133,13.367 133,13.5 c 0,0.133 0.053,0.26 0.146,0.354 0.094,0.093 0.221,0.146 0.354,0.146 h 2 c 0.133,0 0.26,-0.053 0.354,-0.146 C 135.947,13.76 136,13.633 136,13.5 Z m 3,0 c 0,-0.133 -0.053,-0.26 -0.146,-0.354 C 138.76,13.053 138.633,13 138.5,13 h -1 c -0.133,0 -0.26,0.053 -0.354,0.146 C 137.053,13.24 137,13.367 137,13.5 c 0,0.133 0.053,0.26 0.146,0.354 0.094,0.093 0.221,0.146 0.354,0.146 h 1 c 0.133,0 0.26,-0.053 0.354,-0.146 C 138.947,13.76 139,13.633 139,13.5 Z m 4,0 c 0,-0.133 -0.053,-0.26 -0.146,-0.354 C 142.76,13.053 142.633,13 142.5,13 h -2 c -0.133,0 -0.26,0.053 -0.354,0.146 C 140.053,13.24 140,13.367 140,13.5 c 0,0.133 0.053,0.26 0.146,0.354 0.094,0.093 0.221,0.146 0.354,0.146 h 2 c 0.133,0 0.26,-0.053 0.354,-0.146 C 142.947,13.76 143,13.633 143,13.5 Z"
+   sodipodi:nodetypes="sssssssssssccscssssssssscccccccscsscscsscsscsscscsscsscsscscsscs" />
+            </g>
+        </g>
+<path
+   style="fill:none;stroke:#000000;stroke-width:1px;stroke-linecap:round;stroke-linejoin:miter;stroke-opacity:1"
+   d="m 4,6 6.256939,4.520606"
+   id="path4542"
+   inkscape:connector-curvature="0"
+   sodipodi:nodetypes="cc" /><path
+   style="clip-rule:evenodd;fill:none;fill-rule:evenodd;stroke:#000000;stroke-width:1px;stroke-linecap:round;stroke-linejoin:miter;stroke-miterlimit:2;stroke-opacity:1"
+   d="M 12,6 4,12"
+   id="path4542-0"
+   inkscape:connector-curvature="0"
+   sodipodi:nodetypes="cc" /></svg>

toonz/sources/toonz/iocommand.cpp

@@ -322,7 +322,9 @@ bool beforeCellsInsert(TXsheet *xsh, int row, int &col, int rowCount,
   int i              = 0;
   TXshColumn *column = xsh->getColumn(col);
 
-  for (i = 0; i < rowCount && xsh->getCell(row + i, col).isEmpty(); i++) {
+  for (i = 0; i < rowCount && (xsh->getCell(row + i, col).isEmpty() ||
+                               xsh->isImplicitCell(row + i, col));
+       i++) {
   }
   int type = (column && !column->isEmpty()) ? column->getColumnType()
                                             : newLevelColumnType;
@@ -508,8 +510,10 @@ public:
     TXsheet *xsh = TApp::instance()->getCurrentXsheet()->getXsheet();
     for (c = m_col0; c <= m_col1; c++)
       for (r = m_row0; r <= m_row1; r++) {
-        TXshSimpleLevel *oldLevel = xsh->getCell(r, c).getSimpleLevel();
-        TFrameId fid              = xsh->getCell(r, c).getFrameId();
+        TXshCell cell;
+        if (!xsh->isImplicitCell(r, c)) cell = xsh->getCell(r, c);
+        TXshSimpleLevel *oldLevel = cell.getSimpleLevel();
+        TFrameId fid              = cell.getFrameId();
         QPair<int, int> cellId(r, c);
         m_oldLevels[cellId] = QPair<TXshSimpleLevelP, TFrameId>(oldLevel, fid);
       }

toonz/sources/toonz/mainwindow.cpp

@@ -2061,6 +2061,8 @@ void MainWindow::defineActions() {
   createMenuCellsAction(MI_CreateBlankDrawing,
                         QT_TR_NOOP("&Create Blank Drawing"), "Alt+D",
                         "add_cell");
+  createMenuCellsAction(MI_StopFrameHold, QT_TR_NOOP("&Stop Frame Hold"), "",
+                        "stop_frame_hold");
   createMenuCellsAction(MI_Duplicate, QT_TR_NOOP("&Duplicate Drawing  "), "D",
                         "duplicate_drawing");
   createMenuCellsAction(MI_Autorenumber, QT_TR_NOOP("&Autorenumber"), "",
@@ -2501,6 +2503,10 @@ void MainWindow::defineActions() {
   createToggle(MI_ViewerIndicator, QT_TR_NOOP("Toggle Viewer Indicators"), "",
                Preferences::instance()->isViewerIndicatorEnabled(),
                RightClickMenuCommandType);
+  createToggle(MI_ToggleImplicitHold, QT_TR_NOOP("Toggle Implicit Hold"), "",
+               Preferences::instance()->isImplicitHoldEnabled(),
+               MiscCommandType, "implicit_hold",
+               tr("Toggles the implicit hold of a frame to the next frame"));
 
   // Tools
 

toonz/sources/toonz/menubar.cpp

@@ -537,6 +537,7 @@ void TopBar::loadMenubar() {
   addMenuItem(cellsMenu, MI_Autorenumber);
   addMenuItem(cellsMenu, MI_CreateBlankDrawing);
   addMenuItem(cellsMenu, MI_Duplicate);
+  addMenuItem(cellsMenu, MI_StopFrameHold);
   addMenuItem(cellsMenu, MI_MergeFrames);
   addMenuItem(cellsMenu, MI_CloneLevel);
   cellsMenu->addSeparator();

toonz/sources/toonz/menubarcommandids.h

@@ -153,6 +153,7 @@
 #define MI_Autorenumber "MI_Autorenumber"
 #define MI_CreateBlankDrawing "MI_CreateBlankDrawing"
 #define MI_FillEmptyCell "MI_FillEmptyCell"
+#define MI_StopFrameHold "MI_StopFrameHold"
 
 #define MI_MergeFrames "MI_MergeFrames"
 #define MI_Reverse "MI_Reverse"
@@ -478,4 +479,6 @@
 #define MI_ToggleCreationInHoldCells "MI_ToggleCreationInHoldCells"
 #define MI_ToggleAutoStretch "MI_ToggleAutoStretch"
 
+#define MI_ToggleImplicitHold "MI_ToggleImplicitHold"
+
 #endif

toonz/sources/toonz/preferencespopup.cpp

@@ -1062,6 +1062,7 @@ QString PreferencesPopup::getUIString(PreferencesItemId id) {
       {EnableAutoStretch, tr("Enable Auto-stretch Frame")},
       {EnableCreationInHoldCells, tr("Enable Creation in Hold Cells")},
       {EnableAutoRenumber, tr("Enable Autorenumber")},
+      {EnableImplicitHold, tr("Enable Implicit Hold")},
       {vectorSnappingTarget, tr("Vector Snapping:")},
       {saveUnpaintedInCleanup,
        tr("Keep Original Cleaned Up Drawings As Backup")},
@@ -1679,6 +1680,7 @@ QWidget* PreferencesPopup::createDrawingPage() {
   {
     insertUI(NumberingSystem, creationLay, getComboItemList(NumberingSystem));
     insertUI(EnableAutoStretch, creationLay);
+    insertUI(EnableImplicitHold, creationLay);
     insertUI(EnableAutoRenumber, creationLay);
   }
   QGridLayout* autoCreationLay = insertGroupBoxUI(EnableAutocreation, lay);

toonz/sources/toonz/timestretchpopup.cpp

@@ -64,11 +64,13 @@ public:
     assert(nr > 0 && nc > 0);
     m_cells.reset(new TXshCell[nr * nc]);
     assert(m_cells);
-    int k = 0;
+    int k        = 0;
+    TXsheetP xsh = TApp::instance()->getCurrentXsheet()->getXsheet();
     for (int c = c0; c <= c1; c++)
-      for (int r = r0; r <= r1; r++)
-        m_cells[k++] =
-            TApp::instance()->getCurrentXsheet()->getXsheet()->getCell(r, c);
+      for (int r = r0; r <= r1; r++) {
+        const TXshCell &cell = xsh->getCell(r, c);
+        m_cells[k++] = xsh->isImplicitCell(r, c) ? TXshCell() : cell;
+      }
   }
 
   ~TimeStretchUndo() {}
@@ -102,7 +104,7 @@ public:
         for (i = 0; i < nr; i++)
           xsh->setCell(i + m_r0, c, m_cells[i + nr * (c - m_c0)]);
         int dn = oldNr - nr;
-        xsh->removeCells(m_r1, c, dn);
+        xsh->removeCells(m_r1 + 1, c, dn);
       }
     }
 

toonz/sources/toonz/toonz.qrc

@@ -329,8 +329,10 @@
     <file>icons/dark/actions/16/auto_stretch_on.svg</file>
     <file>icons/dark/actions/16/create_in_hold.svg</file>
     <file>icons/dark/actions/16/create_in_hold_on.svg</file>
+    <file>icons/dark/actions/16/implicit_hold.svg</file>
+    <file>icons/dark/actions/16/implicit_hold_on.svg</file>
 
-		<file>icons/dark/actions/16/on_1s.svg</file>
+    <file>icons/dark/actions/16/on_1s.svg</file>
 		<file>icons/dark/actions/16/on_2s.svg</file>
 		<file>icons/dark/actions/16/on_3s.svg</file>
 		<file>icons/dark/actions/16/on_4s.svg</file>
@@ -361,6 +363,7 @@
 		<file>icons/dark/actions/16/remove_cells.svg</file>
 		<file>icons/dark/actions/16/duplicate_drawing.svg</file>
 		<file>icons/dark/actions/16/tracking_options.svg</file>
+		<file>icons/dark/actions/16/stop_frame_hold.svg</file>
 
 		<file>icons/dark/actions/16/camera_settings.svg</file>
 		<file>icons/dark/actions/16/autoexpose.svg</file>

toonz/sources/toonz/xshcellmover.cpp

@@ -201,7 +201,9 @@ bool CellsMover::canMoveCells(const TPoint &pos) {
   int count = 0;
   for (int i = 0; i < m_colCount; i++) {
     for (int j = 0; j < m_rowCount; j++) {
-      if (!xsh->getCell(r + j, c + i).isEmpty()) return false;
+      if (!xsh->getCell(r + j, c + i).isEmpty() &&
+          !xsh->isImplicitCell(r + j, c + i))
+        return false;
       count++;
     }
   }

toonz/sources/toonz/xshcellviewer.cpp

@@ -1880,6 +1880,25 @@ void CellArea::drawFrameMarker(QPainter &p, const QPoint &xy, QColor color,
 
 //-----------------------------------------------------------------------------
 
+void CellArea::drawEndOfLevelMarker(QPainter &p, QRect rect, bool isStopFrame) {
+  const Orientation *o = m_viewer->orientation();
+
+  QColor levelEndColor = m_viewer->getTextColor();
+  QPoint topLeft       = rect.topLeft();
+  QPoint topRight      = rect.topRight();
+  if (!o->isVerticalTimeline() && isStopFrame) {
+    QRect dragRect = o->rect(PredefinedRect::DRAG_AREA);
+    topLeft.setY(topLeft.y() + dragRect.height());
+    topRight.setY(topRight.y() + dragRect.height());
+  }
+  levelEndColor.setAlphaF(0.3);
+  p.setPen(levelEndColor);
+  p.drawLine(topLeft, rect.bottomRight());
+  p.drawLine(topRight, rect.bottomLeft());
+}
+
+//-----------------------------------------------------------------------------
+
 void CellArea::drawLevelCell(QPainter &p, int row, int col, bool isReference,
                              bool showLevelName) {
   const Orientation *o = m_viewer->orientation();
@@ -1907,8 +1926,14 @@ void CellArea::drawLevelCell(QPainter &p, int row, int col, bool isReference,
                     columnSelection->isColumnSelected(col);
   bool isSimpleView = m_viewer->getFrameZoomFactor() <=
                       o->dimension(PredefinedDimension::SCALE_THRESHOLD);
+  bool isImplicitCell = xsh->isImplicitCell(row, col);
+  bool isStopFrame = isImplicitCell ? false : cell.getFrameId().isStopFrame();
 
-  if (row > 0) prevCell = xsh->getCell(row - 1, col);  // cell in previous frame
+  bool prevIsImplicit = false;
+  if (row > 0) {
+    prevCell       = xsh->getCell(row - 1, col);  // cell in previous frame
+    prevIsImplicit = xsh->isImplicitCell(row - 1, col);
+  }
 
   bool sameLevel = prevCell.m_level.getPointer() == cell.m_level.getPointer();
 
@@ -1931,7 +1956,12 @@ void CellArea::drawLevelCell(QPainter &p, int row, int col, bool isReference,
           .translated(QPoint(x, y));
   cellRect.adjust(0, 0, -frameAdj.x(), -frameAdj.y());
   QRect rect = cellRect.adjusted(
-      1, 1, (!o->isVerticalTimeline() && !nextCell.isEmpty() ? 2 : 0), 0);
+      1, 1, (!o->isVerticalTimeline() && !nextCell.isEmpty() &&
+                     !xsh->isImplicitCell(row + 1, col) &&
+                     !nextCell.getFrameId().isStopFrame()
+                 ? 2
+                 : 0),
+      0);
 
   QRect markRect =
       o->rect(PredefinedRect::CELL_MARK_AREA)
@@ -1988,7 +2018,8 @@ void CellArea::drawLevelCell(QPainter &p, int row, int col, bool isReference,
   }
 
   bool heldFrame = (!o->isVerticalTimeline() && sameLevel &&
-                    prevCell.m_frameId == cell.m_frameId);
+                    prevCell.m_frameId == cell.m_frameId) &&
+                   !isImplicitCell;
   drawFrameSeparator(p, row, col, false, heldFrame);
 
   if (cell.isEmpty()) {  // it means previous is not empty
@@ -2001,11 +2032,9 @@ void CellArea::drawLevelCell(QPainter &p, int row, int col, bool isReference,
       p.drawEllipse(markRect);
     }
 
-    QColor levelEndColor = m_viewer->getTextColor();
-    levelEndColor.setAlphaF(0.3);
-    p.setPen(levelEndColor);
-    p.drawLine(rect.topLeft(), rect.bottomRight());
-    p.drawLine(rect.topRight(), rect.bottomLeft());
+    // Implicit holds use Stop Frame Hold to denote end of level
+    if (!Preferences::instance()->isImplicitHoldEnabled())
+      drawEndOfLevelMarker(p, rect);
 
     if (TApp::instance()->getCurrentFrame()->isEditingScene() &&
         !m_viewer->orientation()->isVerticalTimeline() &&
@@ -2024,6 +2053,8 @@ void CellArea::drawLevelCell(QPainter &p, int row, int col, bool isReference,
     int levelType;
     m_viewer->getCellTypeAndColors(levelType, cellColor, sideColor, cell,
                                    isSelected);
+    if (isImplicitCell) cellColor.setAlpha(m_viewer->getImplicitCellAlpha());
+    if (isStopFrame) cellColor.setAlpha(0);
   }
 
   // check if the level is scanned but not cleanupped
@@ -2044,17 +2075,8 @@ void CellArea::drawLevelCell(QPainter &p, int row, int col, bool isReference,
   else
     p.fillRect(rect, QBrush(cellColor));
 
-  if (yetToCleanupCell)  // ORIENTATION: what's this?
-  {
-    if (o->isVerticalTimeline())
-      p.fillRect(rect.adjusted(rect.width() / 2, 0, 0, 0),
-                 (isSelected) ? m_viewer->getSelectedFullcolorColumnColor()
-                              : m_viewer->getFullcolorColumnColor());
-    else
-      p.fillRect(rect.adjusted(0, rect.height() / 2, 0, 0),
-                 (isSelected) ? m_viewer->getSelectedFullcolorColumnColor()
-                              : m_viewer->getFullcolorColumnColor());
-  }
+  // Implicit holds use Stop Frame Hold to denote end of level
+  if (isStopFrame) drawEndOfLevelMarker(p, rect, true);
 
   if (TApp::instance()->getCurrentFrame()->isEditingScene() &&
       !m_viewer->orientation()->isVerticalTimeline() &&
@@ -2062,13 +2084,27 @@ void CellArea::drawLevelCell(QPainter &p, int row, int col, bool isReference,
       Preferences::instance()->isCurrentTimelineIndicatorEnabled())
     drawCurrentTimeIndicator(p, xy);
 
-  drawDragHandle(p, xy, sideColor);
+  if (!isImplicitCell) {
+    if (yetToCleanupCell)  // ORIENTATION: what's this?
+    {
+      if (o->isVerticalTimeline())
+        p.fillRect(rect.adjusted(rect.width() / 2, 0, 0, 0),
+                   (isSelected) ? m_viewer->getSelectedFullcolorColumnColor()
+                                : m_viewer->getFullcolorColumnColor());
+      else
+        p.fillRect(rect.adjusted(0, rect.height() / 2, 0, 0),
+                   (isSelected) ? m_viewer->getSelectedFullcolorColumnColor()
+                                : m_viewer->getFullcolorColumnColor());
+    }
 
-  bool isLastRow = nextCell.isEmpty() ||
-                   cell.m_level.getPointer() != nextCell.m_level.getPointer();
-  drawEndOfDragHandle(p, isLastRow, xy, cellColor);
+    drawDragHandle(p, xy, sideColor);
 
-  drawLockedDottedLine(p, xsh->getColumn(col)->isLocked(), xy, cellColor);
+    bool isLastRow = nextCell.isEmpty() ||
+                     cell.m_level.getPointer() != nextCell.m_level.getPointer();
+    drawEndOfDragHandle(p, isLastRow, xy, cellColor);
+
+    drawLockedDottedLine(p, xsh->getColumn(col)->isLocked(), xy, cellColor);
+  }
 
   int distance, offset;
   TApp::instance()->getCurrentScene()->getScene()->getProperties()->getMarkers(
@@ -2096,11 +2132,13 @@ void CellArea::drawLevelCell(QPainter &p, int row, int col, bool isReference,
   nameRect.adjust(0, 0, -frameAdj.x(), -frameAdj.y());
 
   // draw text in red if the file does not exist
-  bool isRed                                  = false;
-  TXshSimpleLevel *sl                         = cell.getSimpleLevel();
-  if (sl && !sl->isFid(cell.m_frameId)) isRed = true;
-  TXshChildLevel *cl                          = cell.getChildLevel();
-  if (cl && cell.getFrameId().getNumber() - 1 >= cl->getFrameCount())
+  bool isRed          = false;
+  TXshSimpleLevel *sl = cell.getSimpleLevel();
+  if (sl && !cell.getFrameId().isStopFrame() && !sl->isFid(cell.m_frameId))
+    isRed            = true;
+  TXshChildLevel *cl = cell.getChildLevel();
+  if (cl && !cell.getFrameId().isStopFrame() &&
+      cell.getFrameId().getNumber() - 1 >= cl->getFrameCount())
     isRed = true;
   QColor penColor =
       isRed ? QColor(m_viewer->getErrorTextColor()) : m_viewer->getTextColor();
@@ -2124,7 +2162,8 @@ void CellArea::drawLevelCell(QPainter &p, int row, int col, bool isReference,
   // if the same level & same fId with the previous cell,
   // draw continue line
   QString fnum;
-  if (sameLevel && prevCell.m_frameId == cell.m_frameId) {
+  if ((sameLevel && prevCell.m_frameId == cell.m_frameId && !prevIsImplicit) ||
+      isImplicitCell) {
     if (o->isVerticalTimeline()) {
       // not on line marker
       PredefinedLine which =
@@ -2161,7 +2200,8 @@ void CellArea::drawLevelCell(QPainter &p, int row, int col, bool isReference,
         if (pegbar->isKeyframe(row)) return;
       }
 
-      drawFrameMarker(p, QPoint(x, y), (isRed ? Qt::red : Qt::black));
+      if (!isStopFrame)
+        drawFrameMarker(p, QPoint(x, y), (isRed ? Qt::red : Qt::black));
       return;
     }
 
@@ -2169,7 +2209,9 @@ void CellArea::drawLevelCell(QPainter &p, int row, int col, bool isReference,
 
     // convert the last one digit of the frame number to alphabet
     // Ex.  12 -> 1B    21 -> 2A   30 -> 3
-    if (Preferences::instance()->isShowFrameNumberWithLettersEnabled())
+    if (fid.isStopFrame())
+      fnum = "";
+    else if (Preferences::instance()->isShowFrameNumberWithLettersEnabled())
       fnum = m_viewer->getFrameNumberWithLetters(fid.getNumber());
     else {
       QString frameNumber("");
@@ -2180,8 +2222,9 @@ void CellArea::drawLevelCell(QPainter &p, int row, int col, bool isReference,
       fnum = frameNumber;
     }
 
-    int alignFlag =
-        ((showLevelName) ? Qt::AlignRight | Qt::AlignBottom : Qt::AlignCenter);
+    int alignFlag = ((showLevelName && !fid.isStopFrame())
+                         ? Qt::AlignRight | Qt::AlignBottom
+                         : Qt::AlignCenter);
     p.drawText(nameRect, alignFlag, fnum);
   }
 
@@ -2193,9 +2236,11 @@ void CellArea::drawLevelCell(QPainter &p, int row, int col, bool isReference,
     p.setPen(penColor);
   }
 
+  if (isImplicitCell || isStopFrame) return;
+
   // draw level name
   if (showLevelName &&
-      (!sameLevel ||
+      (!sameLevel || (row > 0 && xsh->isImplicitCell(row - 1, col)) ||
        (isAfterMarkers && !isSimpleView &&
         Preferences::instance()->isLevelNameOnEachMarkerEnabled()))) {
     std::wstring levelName = cell.m_level->getName();
@@ -2285,11 +2330,7 @@ void CellArea::drawSoundTextCell(QPainter &p, int row, int col) {
   drawFrameSeparator(p, row, col, false, heldFrame);
 
   if (cell.isEmpty()) {  // diagonal cross meaning end of level
-    QColor levelEndColor = m_viewer->getTextColor();
-    levelEndColor.setAlphaF(0.3);
-    p.setPen(levelEndColor);
-    p.drawLine(rect.topLeft(), rect.bottomRight());
-    p.drawLine(rect.topRight(), rect.bottomLeft());
+    drawEndOfLevelMarker(p, rect);
 
     // only draw mark
     if (markId >= 0) {
@@ -2512,13 +2553,7 @@ void CellArea::drawSoundTextColumn(QPainter &p, int r0, int r1, int col) {
       // draw X shape after the occupied cell
       TXshCell prevCell;
       if (row > 0) prevCell = xsh->getCell(row - 1, col);
-      if (!prevCell.isEmpty()) {
-        QColor levelEndColor = m_viewer->getTextColor();
-        levelEndColor.setAlphaF(0.3);
-        p.setPen(levelEndColor);
-        p.drawLine(info.rect.topLeft(), info.rect.bottomRight());
-        p.drawLine(info.rect.topRight(), info.rect.bottomLeft());
-      }
+      if (!prevCell.isEmpty()) drawEndOfLevelMarker(p, info.rect);
       if (TApp::instance()->getCurrentFrame()->isEditingScene() &&
           !m_viewer->orientation()->isVerticalTimeline() &&
           row == m_viewer->getCurrentRow() &&
@@ -2687,6 +2722,8 @@ void CellArea::drawPaletteCell(QPainter &p, int row, int col,
 
   TCellSelection *cellSelection = m_viewer->getCellSelection();
   bool isSelected               = cellSelection->isCellSelected(row, col);
+  bool isImplicitCell           = xsh->isImplicitCell(row, col);
+  bool isStopFrame = isImplicitCell ? false : cell.getFrameId().isStopFrame();
 
   if (row > 0) prevCell = xsh->getCell(row - 1, col);
   TXshCell nextCell     = xsh->getCell(row + 1, col);
@@ -2722,7 +2759,9 @@ void CellArea::drawPaletteCell(QPainter &p, int row, int col,
   cellRect.adjust(0, 0, -frameAdj.x(), -frameAdj.y());
   QRect rect = cellRect.adjusted(
       1, 1,
-      (!m_viewer->orientation()->isVerticalTimeline() && !nextCell.isEmpty()
+      (!m_viewer->orientation()->isVerticalTimeline() && !nextCell.isEmpty() &&
+               !xsh->isImplicitCell(row + 1, col) &&
+               !nextCell.getFrameId().isStopFrame()
            ? 2
            : 0),
       0);
@@ -2758,15 +2797,14 @@ void CellArea::drawPaletteCell(QPainter &p, int row, int col,
   }
 
   bool heldFrame = (!o->isVerticalTimeline() && !isAfterMarkers && sameLevel &&
-                    prevCell.m_frameId == cell.m_frameId);
+                    prevCell.m_frameId == cell.m_frameId) &&
+                   !isImplicitCell;
   drawFrameSeparator(p, row, col, false, heldFrame);
 
   if (cell.isEmpty()) {  // this means the former is not empty
-    QColor levelEndColor = m_viewer->getTextColor();
-    levelEndColor.setAlphaF(0.3);
-    p.setPen(levelEndColor);
-    p.drawLine(rect.topLeft(), rect.bottomRight());
-    p.drawLine(rect.topRight(), rect.bottomLeft());
+    // Implicit holds use Stop Frame Hold to denote end of level
+    if (!Preferences::instance()->isImplicitHoldEnabled())
+      drawEndOfLevelMarker(p, rect);
 
     // only draw mark
     if (markId >= 0) {
@@ -2780,12 +2818,6 @@ void CellArea::drawPaletteCell(QPainter &p, int row, int col,
         Preferences::instance()->isCurrentTimelineIndicatorEnabled())
       drawCurrentTimeIndicator(p, xy);
 
-    // only draw mark
-    if (markId >= 0) {
-      p.setBrush(markColor);
-      p.setPen(Qt::NoPen);
-      p.drawEllipse(markRect);
-    }
     return;
   }
 
@@ -2798,6 +2830,8 @@ void CellArea::drawPaletteCell(QPainter &p, int row, int col,
     cellColor = (isSelected) ? m_viewer->getSelectedPaletteColumnColor()
                              : m_viewer->getPaletteColumnColor();
     sideColor = m_viewer->getPaletteColumnBorderColor();
+    if (isImplicitCell) cellColor.setAlpha(m_viewer->getImplicitCellAlpha());
+    if (isStopFrame) cellColor.setAlpha(0);
   }
 
   // paint cell
@@ -2809,26 +2843,31 @@ void CellArea::drawPaletteCell(QPainter &p, int row, int col,
   else
     p.fillRect(rect, QBrush(cellColor));
 
+  // Implicit holds use Stop Frame Hold to denote end of level
+  if (isStopFrame) drawEndOfLevelMarker(p, rect, true);
+
   if (TApp::instance()->getCurrentFrame()->isEditingScene() &&
       !m_viewer->orientation()->isVerticalTimeline() &&
       row == m_viewer->getCurrentRow() &&
       Preferences::instance()->isCurrentTimelineIndicatorEnabled())
     drawCurrentTimeIndicator(p, xy);
 
-  drawDragHandle(p, xy, sideColor);
-  bool isLastRow = nextCell.isEmpty() ||
-                   cell.m_level.getPointer() != nextCell.m_level.getPointer();
-  drawEndOfDragHandle(p, isLastRow, xy, cellColor);
-  drawLockedDottedLine(p, xsh->getColumn(col)->isLocked(), xy, cellColor);
+  if (!isImplicitCell) {
+    drawDragHandle(p, xy, sideColor);
+    bool isLastRow = nextCell.isEmpty() ||
+                     cell.m_level.getPointer() != nextCell.m_level.getPointer();
+    drawEndOfDragHandle(p, isLastRow, xy, cellColor);
+    drawLockedDottedLine(p, xsh->getColumn(col)->isLocked(), xy, cellColor);
+  }
 
   if (o->isVerticalTimeline() && isAfterMarkers) {
     p.setPen(m_viewer->getMarkerLineColor());
     p.drawLine(o->line(PredefinedLine::SEE_MARKER_THROUGH).translated(xy));
   }
 
-  if (sameLevel && prevCell.m_frameId == cell.m_frameId &&
-      !isAfterMarkers) {  // cell equal to previous one (not on marker line):
-                          // do not write anything and draw a vertical line
+  if ((sameLevel && prevCell.m_frameId == cell.m_frameId && !isAfterMarkers) ||
+      isImplicitCell) {  // cell equal to previous one (not on marker line):
+                         // do not write anything and draw a vertical line
     if (o->isVerticalTimeline()) {
       QPen oldPen = p.pen();
       p.setPen(QPen(m_viewer->getTextColor(), 1));
@@ -2852,7 +2891,8 @@ void CellArea::drawPaletteCell(QPainter &p, int row, int col,
         TStageObject *pegbar = xsh->getStageObject(m_viewer->getObjectId(col));
         if (pegbar->isKeyframe(row)) return;
       }
-      drawFrameMarker(p, QPoint(x, y), (isRed ? Qt::red : Qt::black));
+      if (!isStopFrame)
+        drawFrameMarker(p, QPoint(x, y), (isRed ? Qt::red : Qt::black));
       return;
     }
 
@@ -2905,10 +2945,15 @@ void CellArea::drawPaletteCell(QPainter &p, int row, int col,
       } else {
         QString frameNumber("");
         // set number
-        if (fid.getNumber() > 0) frameNumber = QString::number(fid.getNumber());
+        if (fid.isStopFrame())
+          frameNumber = "";
+        else if (fid.getNumber() > 0)
+          frameNumber = QString::number(fid.getNumber());
         // add letter
         if (!fid.getLetter().isEmpty()) frameNumber += fid.getLetter();
-        p.drawText(nameRect, Qt::AlignRight | Qt::AlignBottom, frameNumber);
+        int alignFlag = (!fid.isStopFrame() ? Qt::AlignRight | Qt::AlignBottom
+                                            : Qt::AlignCenter);
+        p.drawText(nameRect, alignFlag, frameNumber);
       }
     }
 
@@ -2970,9 +3015,9 @@ void CellArea::drawKeyframe(QPainter &p, const QRect toBeUpdated) {
     row0 = std::max(row0, r0);
     row1 = std::min(row1, r1);
 
-    QRect tmpKeyRect = (col >= 0) ? keyRect
-                                  : o->rect(PredefinedRect::CAMERA_KEY_ICON)
-                                        .translated(-frameAdj / 2);
+    QRect tmpKeyRect =
+        (col >= 0) ? keyRect : o->rect(PredefinedRect::CAMERA_KEY_ICON)
+                                   .translated(-frameAdj / 2);
 
     /*- first, draw key segments -*/
     p.setPen(m_viewer->getTextColor());
@@ -3443,7 +3488,8 @@ void CellArea::mousePressEvent(QMouseEvent *event) {
       m_viewer->getKeyframeSelection()->selectNone();
       setDragTool(
           XsheetGUI::DragTool::makeLevelExtenderTool(m_viewer, false, true));
-    } else if ((!xsh->getCell(row, col).isEmpty()) &&
+    } else if ((!xsh->getCell(row, col).isEmpty() &&
+                !xsh->isImplicitCell(row, col)) &&
                o->rect(PredefinedRect::DRAG_AREA)
                    .adjusted(0, 0, -frameAdj.x(), -frameAdj.y())
                    .contains(mouseInCell)) {
@@ -3714,7 +3760,7 @@ void CellArea::contextMenuEvent(QContextMenuEvent *event) {
   int row                   = cellPosition.frame();
   int col                   = cellPosition.layer();
   TXshCell cell             = m_viewer->getXsheet()->getCell(row, col);
-
+  bool isImplicitCell       = m_viewer->getXsheet()->isImplicitCell(row, col);
   QMenu menu(this);
 
   // Verifico se ho cliccato su una nota
@@ -3783,13 +3829,13 @@ void CellArea::contextMenuEvent(QContextMenuEvent *event) {
         }
       if (areCellsEmpty) break;
     }
-    createCellMenu(menu, areCellsEmpty, cell, row, col);
+    createCellMenu(menu, areCellsEmpty, cell, row, col, isImplicitCell);
   } else {
     m_viewer->getCellSelection()->makeCurrent();
     m_viewer->getCellSelection()->selectCell(row, col);
     m_viewer->setCurrentColumn(col);
 
-    createCellMenu(menu, !cell.isEmpty(), cell, row, col);
+    createCellMenu(menu, !cell.isEmpty(), cell, row, col, isImplicitCell);
   }
 
   if (!menu.isEmpty()) menu.exec(event->globalPos());
@@ -3879,7 +3925,7 @@ const bool CellArea::isControlPressed() { return isCtrlPressed; }
 
 //-----------------------------------------------------------------------------
 void CellArea::createCellMenu(QMenu &menu, bool isCellSelected, TXshCell cell,
-                              int row, int col) {
+                              int row, int col, bool isImplicitCell) {
   CommandManager *cmdManager = CommandManager::instance();
 
   bool soundCellsSelected     = m_viewer->areSoundCellsSelected();
@@ -3952,11 +3998,13 @@ void CellArea::createCellMenu(QMenu &menu, bool isCellSelected, TXshCell cell,
         }
         menu.addMenu(editCellNumbersMenu);
       }
+
       menu.addAction(cmdManager->getAction(MI_FillEmptyCell));
+      menu.addAction(cmdManager->getAction(MI_StopFrameHold));
 
       menu.addSeparator();
 
-      if (!soundTextCellsSelected)
+      if (!soundTextCellsSelected && !isImplicitCell)
         menu.addAction(cmdManager->getAction(MI_Autorenumber));
     }
 
@@ -3997,17 +4045,19 @@ void CellArea::createCellMenu(QMenu &menu, bool isCellSelected, TXshCell cell,
             replaceMenu->addAction(tmpAction);
           }
         }
+        if (!soundCellsSelected && !soundTextCellsSelected) {
+          if (selectionContainTlvImage(m_viewer->getCellSelection(),
+                                       m_viewer->getXsheet()))
+            replaceLevelMenu->addAction(
+                cmdManager->getAction(MI_RevertToCleanedUp));
+          if (selectionContainLevelImage(m_viewer->getCellSelection(),
+                                         m_viewer->getXsheet()))
+            replaceLevelMenu->addAction(
+                cmdManager->getAction(MI_RevertToLastSaved));
+        }
       }
 
       if (!soundCellsSelected && !soundTextCellsSelected) {
-        if (selectionContainTlvImage(m_viewer->getCellSelection(),
-                                     m_viewer->getXsheet()))
-          replaceLevelMenu->addAction(
-              cmdManager->getAction(MI_RevertToCleanedUp));
-        if (selectionContainLevelImage(m_viewer->getCellSelection(),
-                                       m_viewer->getXsheet()))
-          replaceLevelMenu->addAction(
-              cmdManager->getAction(MI_RevertToLastSaved));
         menu.addAction(cmdManager->getAction(MI_SetKeyframes));
         menu.addAction(cmdManager->getAction(MI_ShiftKeyframesDown));
         menu.addAction(cmdManager->getAction(MI_ShiftKeyframesUp));
@@ -4015,8 +4065,10 @@ void CellArea::createCellMenu(QMenu &menu, bool isCellSelected, TXshCell cell,
       menu.addSeparator();
     }
 
-    menu.addAction(cmdManager->getAction(MI_Cut));
-    menu.addAction(cmdManager->getAction(MI_Copy));
+    if (!isImplicitCell) {
+      menu.addAction(cmdManager->getAction(MI_Cut));
+      menu.addAction(cmdManager->getAction(MI_Copy));
+    }
     menu.addAction(cmdManager->getAction(MI_Paste));
 
     QMenu *pasteSpecialMenu = new QMenu(tr("Paste Special"), this);
@@ -4029,7 +4081,7 @@ void CellArea::createCellMenu(QMenu &menu, bool isCellSelected, TXshCell cell,
     }
     menu.addMenu(pasteSpecialMenu);
 
-    menu.addAction(cmdManager->getAction(MI_Clear));
+    if (!isImplicitCell) menu.addAction(cmdManager->getAction(MI_Clear));
     menu.addAction(cmdManager->getAction(MI_Insert));
     if (!soundTextCellsSelected) {
       menu.addAction(cmdManager->getAction(MI_CreateBlankDrawing));
@@ -4086,6 +4138,7 @@ void CellArea::createCellMenu(QMenu &menu, bool isCellSelected, TXshCell cell,
     menu.addAction(cmdManager->getAction(MI_CreateBlankDrawing));
     menu.addSeparator();
     menu.addAction(cmdManager->getAction(MI_FillEmptyCell));
+    menu.addAction(cmdManager->getAction(MI_StopFrameHold));
     if (cameraCellsSelected) {
       menu.addSeparator();
       menu.addAction(cmdManager->getAction(MI_SetKeyframes));
@@ -4131,6 +4184,7 @@ void CellArea::createCellMenu(QMenu &menu, bool isCellSelected, TXshCell cell,
   menu.addAction(cmdManager->getAction(MI_ToggleAutoCreate));
   menu.addAction(cmdManager->getAction(MI_ToggleCreationInHoldCells));
   menu.addAction(cmdManager->getAction(MI_ToggleAutoStretch));
+  menu.addAction(cmdManager->getAction(MI_ToggleImplicitHold));
 }
 
 //-----------------------------------------------------------------------------
@@ -4160,7 +4214,7 @@ void CellArea::onReplaceByCastedLevel(QAction *action) {
       if (!cell.m_level.getPointer() || cell.m_level.getPointer() == level)
         continue;
 
-      TXshCell oldCell = cell;
+      TXshCell oldCell = xsh->isImplicitCell(r, c) ? TXshCell() : cell;
 
       cell.m_level = TXshLevelP(level);
       xsh->setCell(r, c, cell);

toonz/sources/toonz/xshcellviewer.h

@@ -131,6 +131,7 @@ class CellArea final : public QWidget {
 
   void drawFrameMarker(QPainter &p, const QPoint &xy, QColor color,
                        bool isKeyFrame = false, bool isCamera = false);
+  void drawEndOfLevelMarker(QPainter &p, QRect rect, bool isStopFrame = false);
 
   // Restistusce true
   bool getEaseHandles(int r0, int r1, double e0, double e1, int &rh0, int &rh1);
@@ -183,7 +184,7 @@ protected:
 cella,
 distinguendo i due casi: cella piena, cella vuota.*/
   void createCellMenu(QMenu &menu, bool isCellSelected, TXshCell cell, int row,
-                      int col);
+                      int col, bool isImplicitCell);
   //! Crea il menu' del tasto destro che si visualizza si clicca su un key
   //! frame.
   void createKeyMenu(QMenu &menu);

toonz/sources/toonz/xshcolumnviewer.cpp

@@ -102,7 +102,7 @@ bool containsRasterLevel(TColumnSelection *selection) {
     if (!cellCol) continue;
 
     int i;
-    for (i = 0; i < cellCol->getMaxFrame() + 1; i++) {
+    for (i = 0; i < cellCol->getMaxFrame(true) + 1; i++) {
       TXshCell cell = cellCol->getCell(i);
       if (cell.isEmpty()) continue;
       TXshSimpleLevel *level = cell.getSimpleLevel();

toonz/sources/toonz/xsheetcmd.cpp

@@ -169,7 +169,10 @@ void InsertSceneFrameUndo::doInsertSceneFrame(int frame) {
       objectId = TStageObjectId::ColumnId(c);
 
       xsh->insertCells(frame, c);
-      xsh->setCell(frame, c, xsh->getCell(frame + 1, c));
+      TXshCell cell;
+      if (!Preferences::instance()->isImplicitHoldEnabled() && frame > 0)
+        cell = xsh->getCell(frame - 1, c);
+      xsh->setCell(frame, c, cell);
     }
 
     if (!xsh->getColumn(c) || xsh->getColumn(c)->isLocked()) continue;
@@ -288,6 +291,24 @@ public:
   }
 } ToggleAutoStretchCommand;
 
+//=============================================================================
+
+class ToggleImplicitHoldCommand final : public MenuItemHandler {
+public:
+  ToggleImplicitHoldCommand() : MenuItemHandler(MI_ToggleImplicitHold) {}
+  void execute() override {
+    bool currentImplicitHoldEnabled =
+        Preferences::instance()->isImplicitHoldEnabled();
+    if (CommandManager::instance()
+            ->getAction(MI_ToggleImplicitHold)
+            ->isChecked() == currentImplicitHoldEnabled)
+      return;
+    Preferences::instance()->setValue(EnableImplicitHold,
+                                      !currentImplicitHoldEnabled);
+    TApp::instance()->getCurrentXsheet()->notifyXsheetChanged();
+  }
+} ToggleImplicitHoldCommand;
+
 //*****************************************************************************
 //    RemoveSceneFrame  command
 //*****************************************************************************
@@ -314,7 +335,8 @@ public:
 
     for (int c = 0; c != colsCount; ++c) {
       // Store cell
-      m_cells[c] = xsh->getCell(m_frame, c);
+      const TXshCell &cell = xsh->getCell(m_frame, c);
+      m_cells[c] = xsh->isImplicitCell(m_frame, c) ? TXshCell() : cell;
 
       // Store stage object keyframes
       TStageObject *obj = xsh->getStageObject(TStageObjectId::ColumnId(c));
@@ -638,9 +660,10 @@ public:
     int r = m_range.m_r0;
     while (c <= m_range.m_c1) {
       tempCol = c;
-      while (r <= m_range.m_r1) {
+      while (r <= m_range.m_r1 + 1) {
         tempRow = r;
-        if (xsh->getCell(tempRow, tempCol).isEmpty()) {
+        if (xsh->getCell(tempRow, tempCol).isEmpty() ||
+            xsh->isImplicitCell(tempRow, tempCol)) {
           emptyCells.push_back(std::make_pair(tempRow, tempCol));
         }
         r++;
@@ -664,7 +687,7 @@ public:
     int r = m_range.m_r0;
     while (c <= m_range.m_c1) {
       col = c;
-      while (r <= m_range.m_r1) {
+      while (r <= m_range.m_r1 + 1) {
         row        = r;
         bool found = false;
         for (int i = 0; i < emptyCells.size(); i++) {
@@ -677,7 +700,7 @@ public:
           r++;
           continue;
         }
-        changeDrawing(-m_direction, row, col);
+        if (r <= m_range.m_r1) changeDrawing(-m_direction, row, col);
         r++;
       }
       r = m_range.m_r0;
@@ -698,11 +721,18 @@ public:
     int col, row;
     int c = m_range.m_c0;
     int r = m_range.m_r0;
+    TXsheetP xsh = TApp::instance()->getCurrentXsheet()->getXsheet();
     while (c <= m_range.m_c1) {
       col = c;
+      // Convert implicit cell at end of selected range into a populated cell
+      if (xsh->isImplicitCell((m_range.m_r1 + 1), col)) {
+        TXshCell origCell = xsh->getCell((m_range.m_r1 + 1), col);
+        xsh->setCell((m_range.m_r1 + 1), col, origCell);
+      }
       while (r <= m_range.m_r1) {
         row = r;
-        changeDrawing(m_direction, row, col);
+        if (row == m_range.m_r0 || !xsh->isImplicitCell(row, col))
+          changeDrawing(m_direction, row, col);
         r++;
       }
       r = m_range.m_r0;
@@ -766,13 +796,16 @@ public:
 
         // Find the 1st populated cell in the column
         if (baseCell.isEmpty()) continue;
+        if (xsh->isImplicitCell(r, c))
+          emptyCells.push_back(std::make_pair(r, c));
 
         FramesMap::key_type frameBaseKey(r, c);
         int frameCount    = 1;
         TXshCell nextCell = xsh->getCell((r + frameCount), c);
         while (nextCell == baseCell ||
                (nextCell.isEmpty() && (r + frameCount) <= m_range.m_r1)) {
-          if (nextCell.isEmpty())
+          if ((r + frameCount) >= xsh->getFrameCount()) break;
+          if (nextCell.isEmpty() || xsh->isImplicitCell((r + frameCount), c))
             emptyCells.push_back(std::make_pair((r + frameCount), c));
 
           frameCount++;
@@ -820,7 +853,10 @@ public:
       while (n < ct->second) {
         int row = ct->first.first + n;
         int col = ct->first.second;
-        DrawingSubtitutionUndo::changeDrawing(m_direction, row, col);
+        if (n == 0 ||
+            !TApp::instance()->getCurrentXsheet()->getXsheet()->isImplicitCell(
+                row, col))
+          DrawingSubtitutionUndo::changeDrawing(m_direction, row, col);
         n++;
       }
     }
@@ -853,10 +889,12 @@ bool DrawingSubtitutionUndo::changeDrawing(int delta, int row, int col) {
       return false;
     cell        = prevCell;
     usePrevCell = true;
-  } else if (!cell.m_level || !(cell.m_level->getSimpleLevel() ||
-                                cell.m_level->getChildLevel() ||
-                                cell.m_level->getSoundTextLevel()))
+  } else if (cell.getFrameId().isStopFrame() || !cell.m_level ||
+             !(cell.m_level->getSimpleLevel() ||
+               cell.m_level->getChildLevel() ||
+               cell.m_level->getSoundTextLevel()))
     return false;
+
   TXshLevel *level = cell.m_level->getSimpleLevel();
   if (!level) level = cell.m_level->getChildLevel();
   if (!level) level = cell.m_level->getSoundTextLevel();
@@ -2316,11 +2354,10 @@ public:
 
         while (!exit) {
             TXshCell cell = TApp::instance()->getCurrentXsheetViewer()->getXsheet()->getCell(currentPos, column);
-            if (cell.isEmpty()) {
+            if (cell.isEmpty() || cell.getFrameId().isStopFrame()) {
                 (direction == up) ? currentPos++ : currentPos--;
                 exit = true;
-            }
-            else
+            } else
                 (direction == up) ? currentPos-- : currentPos++;
         }
 
@@ -2328,15 +2365,19 @@ public:
     }
 
     void execute() override {
-        int col = TApp::instance()->getCurrentColumn()->getColumnIndex();
-        int row = TApp::instance()->getCurrentFrame()->getFrame();
-        TXshCell cell =
-            TApp::instance()->getCurrentXsheetViewer()->getXsheet()->getCell(row, col);
-        if (cell.isEmpty()) return;
+        int col       = TApp::instance()->getCurrentColumn()->getColumnIndex();
+        int row       = TApp::instance()->getCurrentFrame()->getFrame();
+        TXsheet *xsh  = TApp::instance()->getCurrentXsheetViewer()->getXsheet();
+        TXshCell cell = xsh->getCell(row, col);
+        if (cell.isEmpty() || cell.getFrameId().isStopFrame()) return;
         int step, r0, r1;
 
+        xsh->getCellRange(col, r0, r1);
+
         int top = getNonEmptyCell(row, col, Direction::up);
-        int bottom = getNonEmptyCell(row, col, Direction::down);
+        int bottom = (xsh->isImplicitCell(row, col) && row > r1)
+                         ? row
+                         : getNonEmptyCell(row, col, Direction::down);
 
         XsheetGUI::getPlayRange(r0, r1, step);
         XsheetGUI::setPlayRange(top, bottom, step);

toonz/sources/toonz/xsheetdragtool.cpp

@@ -2063,7 +2063,8 @@ protected:
         getViewer()->orientation()->isVerticalTimeline());
     for (c = col; c < rect.getLx() + col; c++) {
       for (r = row; r < rect.getLy() + row; r++)
-        if (!xsh->getCell(r, c).isEmpty()) return false;
+        if (!xsh->getCell(r, c).isEmpty() && !xsh->isImplicitCell(r, c))
+          return false;
     }
     return true;
   }

toonz/sources/toonz/xsheetviewer.h

@@ -349,6 +349,11 @@ class XsheetViewer final : public QFrame, public SaveLoadQSettings {
   Q_PROPERTY(QColor SelectedMeshColumnColor READ getSelectedMeshColumnColor
                  WRITE setSelectedMeshColumnColor)
 
+  // Implicit Cell alpha
+  int m_implicitCellAlpha;
+  Q_PROPERTY(int ImplicitCellAlpha READ getImplicitCellAlpha WRITE
+                 setImplicitCellAlpha);
+
   // Table color
   QColor m_tableColor;
   Q_PROPERTY(QColor TableColor READ getTableColor WRITE setTableColor)
@@ -949,6 +954,10 @@ public:
     return m_selectedMeshColumnColor;
   }
 
+  // Implicit Cell Alpha
+  void setImplicitCellAlpha(const int &alpha) { m_implicitCellAlpha = alpha; }
+  int getImplicitCellAlpha() const { return m_implicitCellAlpha; }
+
   // Table node
   void setTableColor(const QColor &color) { m_tableColor = color; }
   QColor getTableColor() const { return m_tableColor; }

toonz/sources/toonz/xshrowviewer.cpp

@@ -1272,7 +1272,7 @@ void RowArea::contextMenuEvent(QContextMenuEvent *event) {
 bool RowArea::canSetAutoMarkers() {
   TXshCell cell =
       m_viewer->getXsheet()->getCell(m_row, m_viewer->getCurrentColumn());
-  return cell.isEmpty() ? false : true;
+  return cell.isEmpty() || cell.getFrameId().isStopFrame() ? false : true;
 }
 
 //-----------------------------------------------------------------------------

toonz/sources/toonzlib/fxcommand.cpp

@@ -16,6 +16,7 @@
 #include "toonz/tfxhandle.h"
 #include "toonz/tcolumnhandle.h"
 #include "toonz/tscenehandle.h"
+#include "toonz/preferences.h"
 #include "historytypes.h"
 
 // TnzBase includes
@@ -309,7 +310,9 @@ TXshZeraryFxColumn *FxCommandUndo::createZeraryFxColumn(TXsheet *xsh, TFx *zfx,
   int frameCount = xsh->getScene()->getFrameCount() - row;
 
   TXshZeraryFxColumn *column =
-      new TXshZeraryFxColumn(frameCount > 0 ? frameCount : 100);
+      new TXshZeraryFxColumn(Preferences::instance()->isImplicitHoldEnabled()
+                                 ? 1
+                                 : (frameCount > 0 ? frameCount : 100));
   column->getZeraryColumnFx()->setZeraryFx(zfx);
   column->insertEmptyCells(0, row);
 
@@ -2541,7 +2544,9 @@ void UndoPasteFxs::initialize(const std::map<TFx *, int> &zeraryFxColumnSize,
       // column with
       // the specified column size
       std::map<TFx *, int>::const_iterator it = zeraryFxColumnSize.find(fx);
-      int rows = (it == zeraryFxColumnSize.end()) ? 100 : it->second;
+      int rows = Preferences::instance()->isImplicitHoldEnabled()
+                     ? 1
+                     : ((it == zeraryFxColumnSize.end()) ? 100 : it->second);
 
       TXshZeraryFxColumn *column = new TXshZeraryFxColumn(rows);
       TZeraryColumnFx *zcfx      = column->getZeraryColumnFx();

toonz/sources/toonzlib/preferences.cpp

@@ -512,7 +512,8 @@ void Preferences::definePreferenceItems() {
 
   define(EnableAutocreation, "EnableAutocreation", QMetaType::Bool, true);
   define(NumberingSystem, "NumberingSystem", QMetaType::Int, 0);  // Incremental
-  define(EnableAutoStretch, "EnableAutoStretch", QMetaType::Bool, true);
+  define(EnableAutoStretch, "EnableAutoStretch", QMetaType::Bool, false);
+  define(EnableImplicitHold, "EnableImplicitHold", QMetaType::Bool, true);
   define(EnableCreationInHoldCells, "EnableCreationInHoldCells",
          QMetaType::Bool, true);
   define(EnableAutoRenumber, "EnableAutoRenumber", QMetaType::Bool, true);

toonz/sources/toonzlib/scenefx.cpp

@@ -111,6 +111,15 @@ public:
     if (!m_cellColumn) return m_frame;
     TXshCell cell = m_cellColumn->getCell(tfloor(frame));
     assert(!cell.isEmpty());
+    if (cell.isEmpty() && Preferences::instance()->isImplicitHoldEnabled()) {
+      int r0, r1;
+      m_cellColumn->getRange(r0, r1);
+      for (int r = std::min(r1, frame); r >= r0; r--) {
+        cell = m_cellColumn->getCell(r);
+        if (cell.isEmpty()) continue;
+        break;
+      }
+    }
     return cell.m_frameId.getNumber() - 1;
   }
 
@@ -801,6 +810,15 @@ PlacedFx FxBuilder::makePF(TLevelColumnFx *lcfx) {
   // Retrieve the corresponding xsheet cell to build up
   /*-- 現在のフレームのセルを取得 --*/
   TXshCell cell  = lcfx->getColumn()->getCell(tfloor(m_frame));
+  if (cell.isEmpty() && Preferences::instance()->isImplicitHoldEnabled()) {
+    int r0, r1;
+    lcfx->getColumn()->getRange(r0, r1);
+    for (int r = std::min(r1, tfloor(m_frame)); r >= r0; r--) {
+      cell = lcfx->getColumn()->getCell(r);
+      if (cell.isEmpty()) continue;
+      break;
+    }
+  }
   int levelFrame = cell.m_frameId.getNumber() - 1;
 
   /*--  ParticlesFxに繋がっておらず、空セルの場合は 中身無しを返す --*/
@@ -940,7 +958,17 @@ PlacedFx FxBuilder::makePF(TPaletteColumnFx *pcfx) {
   if (!pcfx->getColumn()->isPreviewVisible()) return PlacedFx();
 
   TXshCell cell = pcfx->getColumn()->getCell(tfloor(m_frame));
-  if (cell.isEmpty()) return PlacedFx();
+  if (cell.isEmpty() && Preferences::instance()->isImplicitHoldEnabled()) {
+    int r0, r1;
+    pcfx->getColumn()->getRange(r0, r1);
+    for (int r = std::min(r1, tfloor(m_frame)); r >= r0; r--) {
+      cell = pcfx->getColumn()->getCell(r);
+      if (cell.isEmpty()) continue;
+      break;
+    }
+  }
+
+  if (cell.isEmpty() || cell.getFrameId().isStopFrame()) return PlacedFx();
 
   PlacedFx pf;
   pf.m_columnIndex = pcfx->getColumn()->getIndex();
@@ -968,6 +996,15 @@ PlacedFx FxBuilder::makePF(TZeraryColumnFx *zcfx) {
     return PlacedFx();
 
   TXshCell cell = zcfx->getColumn()->getCell(tfloor(m_frame));
+  if (cell.isEmpty() && Preferences::instance()->isImplicitHoldEnabled()) {
+    int r0, r1;
+    zcfx->getColumn()->getRange(r0, r1);
+    for (int r = std::min(r1, tfloor(m_frame)); r >= r0; r--) {
+      cell = zcfx->getColumn()->getCell(r);
+      if (cell.isEmpty()) continue;
+      break;
+    }
+  }
 
   // Build
   PlacedFx pf;
@@ -978,7 +1015,7 @@ PlacedFx FxBuilder::makePF(TZeraryColumnFx *zcfx) {
     return PlacedFx();
 
   // if the cell is empty, only inherits its placement
-  if (cell.isEmpty()) return pf;
+  if (cell.isEmpty() || cell.getFrameId().isStopFrame()) return pf;
 
   // set m_fx only when the current cell is not empty
   pf.m_fx =

toonz/sources/toonzlib/stage.cpp

@@ -364,22 +364,23 @@ void StageBuilder::addCell(PlayerSet &players, ToonzScene *scene, TXsheet *xsh,
   double columnZ        = pegbar->getZ(row);
   double columnNoScaleZ = pegbar->getGlobalNoScaleZ();
 
-  TXshCell cell = xsh->getCell(row, col);
-  TXshLevel *xl = cell.m_level.getPointer();
+  TXshCell cell       = xsh->getCell(row, col);
+  TXshLevel *xl       = cell.m_level.getPointer();
+  TXshSimpleLevel *sl = xl ? xl->getSimpleLevel() : 0;
   // check the previous row for a stop motion layer
   if (!xl) {
+    // Get the last populated cell
     cell = xsh->getCell(row - 1, col);
     xl   = cell.m_level.getPointer();
-    if (!xl) {
+
+    if (!xl) return;
+
+    sl = xl->getSimpleLevel();
+
+    if (sl && m_liveViewImage && sl == m_liveViewPlayer.m_sl)
+      row -= 1;
+    else
       return;
-    } else {
-      xl                  = cell.m_level.getPointer();
-      TXshSimpleLevel *sl = xl->getSimpleLevel();
-      if (sl && m_liveViewImage && sl == m_liveViewPlayer.m_sl) {
-        row -= 1;
-      } else
-        return;
-    }
   }
 
   ZPlacement cameraPlacement;
@@ -394,8 +395,6 @@ void StageBuilder::addCell(PlayerSet &players, ToonzScene *scene, TXsheet *xsh,
 
   if (!columnBehindCamera) return;
 
-  TXshSimpleLevel *sl = xl->getSimpleLevel();
-
   bool storePlayer =
       sl || (xl->getChildLevel() &&
              locals::applyPlasticDeform(column.getPointer(), m_vs) &&

toonz/sources/toonzlib/tcolumnfx.cpp

@@ -819,7 +819,17 @@ bool TLevelColumnFx::canHandle(const TRenderSettings &info, double frame) {
 
   if (!m_levelColumn) return true;
 
-  TXshCell cell = m_levelColumn->getCell(m_levelColumn->getFirstRow());
+  int row       = m_levelColumn->getFirstRow();
+  TXshCell cell = m_levelColumn->getCell(row);
+  if (cell.isEmpty() && Preferences::instance()->isImplicitHoldEnabled()) {
+    int r0, r1;
+    m_levelColumn->getRange(r0, r1);
+    for (int r = std::min(r1, row); r >= r0; r--) {
+      cell = m_levelColumn->getCell(r);
+      if (cell.isEmpty()) continue;
+      break;
+    }
+  }
   if (cell.isEmpty()) return true;
 
   TXshSimpleLevel *sl = cell.m_level->getSimpleLevel();
@@ -835,7 +845,17 @@ TAffine TLevelColumnFx::handledAffine(const TRenderSettings &info,
                                       double frame) {
   if (!m_levelColumn) return TAffine();
 
-  TXshCell cell = m_levelColumn->getCell(m_levelColumn->getFirstRow());
+  int row       = m_levelColumn->getFirstRow();
+  TXshCell cell = m_levelColumn->getCell(row);
+  if (cell.isEmpty() && Preferences::instance()->isImplicitHoldEnabled()) {
+    int r0, r1;
+    m_levelColumn->getRange(r0, r1);
+    for (int r = std::min(r1, row); r >= r0; r--) {
+      cell = m_levelColumn->getCell(r);
+      if (cell.isEmpty()) continue;
+      break;
+    }
+  }
   if (cell.isEmpty()) return TAffine();
 
   TXshSimpleLevel *sl = cell.m_level->getSimpleLevel();
@@ -873,6 +893,16 @@ TFilePath TLevelColumnFx::getPalettePath(int frame) const {
   if (!m_levelColumn) return TFilePath();
 
   TXshCell cell = m_levelColumn->getCell(frame);
+  if (cell.isEmpty() && Preferences::instance()->isImplicitHoldEnabled()) {
+    int r0, r1;
+    m_levelColumn->getRange(r0, r1);
+    for (int r = std::min(r1, frame); r >= r0; r--) {
+      cell = m_levelColumn->getCell(r);
+      if (cell.isEmpty()) continue;
+      break;
+    }
+  }
+
   if (cell.isEmpty()) return TFilePath();
 
   TXshSimpleLevel *sl = cell.m_level->getSimpleLevel();
@@ -894,6 +924,15 @@ TPalette *TLevelColumnFx::getPalette(int frame) const {
   if (!m_levelColumn) return 0;
 
   TXshCell cell = m_levelColumn->getCell(frame);
+  if (cell.isEmpty() && Preferences::instance()->isImplicitHoldEnabled()) {
+    int r0, r1;
+    m_levelColumn->getRange(r0, r1);
+    for (int r = std::min(r1, frame); r >= r0; r--) {
+      cell = m_levelColumn->getCell(r);
+      if (cell.isEmpty()) continue;
+      break;
+    }
+  }
   if (cell.isEmpty()) return 0;
 
   TXshSimpleLevel *sl = cell.m_level->getSimpleLevel();
@@ -921,6 +960,15 @@ void TLevelColumnFx::doDryCompute(TRectD &rect, double frame,
 
   int row       = (int)frame;
   TXshCell cell = m_levelColumn->getCell(row);
+  if (cell.isEmpty() && Preferences::instance()->isImplicitHoldEnabled()) {
+    int r0, r1;
+    m_levelColumn->getRange(r0, r1);
+    for (int r = std::min(r1, row); r >= r0; r--) {
+      cell = m_levelColumn->getCell(r);
+      if (cell.isEmpty()) continue;
+      break;
+    }
+  }
   if (cell.isEmpty()) return;
 
   TXshSimpleLevel *sl = cell.m_level->getSimpleLevel();
@@ -971,7 +1019,15 @@ void TLevelColumnFx::doCompute(TTile &tile, double frame,
   // Ensure that a corresponding cell and level exists
   int row       = (int)frame;
   TXshCell cell = m_levelColumn->getCell(row);
-
+  if (cell.isEmpty() && Preferences::instance()->isImplicitHoldEnabled()) {
+    int r0, r1;
+    m_levelColumn->getRange(r0, r1);
+    for (int r = std::min(r1, row); r >= r0; r--) {
+      cell = m_levelColumn->getCell(r);
+      if (cell.isEmpty()) continue;
+      break;
+    }
+  }
   if (cell.isEmpty()) return;
 
   TXshSimpleLevel *sl = cell.m_level->getSimpleLevel();
@@ -1388,8 +1444,17 @@ bool TLevelColumnFx::doGetBBox(double frame, TRectD &bBox,
   // Usual preliminaries (make sure a level/cell exists, etc...)
   if (!m_levelColumn) return false;
 
-  int row              = (int)frame;
-  const TXshCell &cell = m_levelColumn->getCell(row);
+  int row       = (int)frame;
+  TXshCell cell = m_levelColumn->getCell(row);
+  if (cell.isEmpty() && Preferences::instance()->isImplicitHoldEnabled()) {
+    int r0, r1;
+    m_levelColumn->getRange(r0, r1);
+    for (int r = std::min(r1, row); r >= r0; r--) {
+      cell = m_levelColumn->getCell(r);
+      if (cell.isEmpty()) continue;
+      break;
+    }
+  }
   if (cell.isEmpty()) return false;
 
   TXshLevelP xshl = cell.m_level;
@@ -1418,7 +1483,17 @@ bool TLevelColumnFx::doGetBBox(double frame, TRectD &bBox,
 
     dpi = imageInfo.m_dpix / Stage::inch;
   } else {
-    TImageP img = m_levelColumn->getCell(row).getImage(false);
+    TXshCell cell = m_levelColumn->getCell(row);
+    if (cell.isEmpty() && Preferences::instance()->isImplicitHoldEnabled()) {
+      int r0, r1;
+      m_levelColumn->getRange(r0, r1);
+      for (int r = std::min(r1, row); r >= r0; r--) {
+        cell = m_levelColumn->getCell(r);
+        if (cell.isEmpty()) continue;
+        break;
+      }
+    }
+    TImageP img = cell.getImage(false);
     if (!img) return false;
     bBox = img->getBBox();
   }
@@ -1484,10 +1559,19 @@ std::wstring TLevelColumnFx::getColumnName() const {
 
 std::string TLevelColumnFx::getAlias(double frame,
                                      const TRenderSettings &info) const {
-  if (!m_levelColumn || m_levelColumn->getCell((int)frame).isEmpty())
-    return std::string();
+  if (!m_levelColumn) return std::string();
 
-  const TXshCell &cell = m_levelColumn->getCell((int)frame);
+  TXshCell cell = m_levelColumn->getCell((int)frame);
+  if (cell.isEmpty() && Preferences::instance()->isImplicitHoldEnabled()) {
+    int r0, r1;
+    m_levelColumn->getRange(r0, r1);
+    for (int r = std::min(r1, (int)frame); r >= r0; r--) {
+      cell = m_levelColumn->getCell(r);
+      if (cell.isEmpty()) continue;
+      break;
+    }
+  }
+  if (cell.isEmpty()) return std::string();
 
   TFilePath fp;
   TXshSimpleLevel *sl = cell.getSimpleLevel();
@@ -1548,6 +1632,15 @@ TAffine TLevelColumnFx::getDpiAff(int frame) {
   if (!m_levelColumn) return TAffine();
 
   TXshCell cell = m_levelColumn->getCell(frame);
+  if (cell.isEmpty() && Preferences::instance()->isImplicitHoldEnabled()) {
+    int r0, r1;
+    m_levelColumn->getRange(r0, r1);
+    for (int r = std::min(r1, frame); r >= r0; r--) {
+      cell = m_levelColumn->getCell(r);
+      if (cell.isEmpty()) continue;
+      break;
+    }
+  }
   if (cell.isEmpty()) return TAffine();
 
   TXshSimpleLevel *sl = cell.m_level->getSimpleLevel();

toonz/sources/toonzlib/txshcolumn.cpp

@@ -36,7 +36,7 @@ TXshCellColumn::~TXshCellColumn() { m_cells.clear(); }
 
 //-----------------------------------------------------------------------------
 
-int TXshCellColumn::getRange(int &r0, int &r1) const {
+int TXshCellColumn::getRange(int &r0, int &r1, bool ignoreLastStop) const {
   int cellCount = m_cells.size();
   r0            = m_first;
   r1            = r0 + cellCount - 1;
@@ -51,8 +51,10 @@ int TXshCellColumn::getRange(int &r0, int &r1) const {
   r0 = m_first + i;
   for (i = cellCount - 1; i >= 0 && m_cells[i].isEmpty(); i--) {
   }
-
   r1 = m_first + i;
+  if (r1 < m_cells.size() && r1 > r0 && ignoreLastStop &&
+      m_cells[r1].getFrameId().isStopFrame())
+    r1--;
   return r1 - r0 + 1;
 }
 
@@ -70,9 +72,9 @@ int TXshCellColumn::getRowCount() const {
 
 //-----------------------------------------------------------------------------
 
-int TXshCellColumn::getMaxFrame() const {
+int TXshCellColumn::getMaxFrame(bool ignoreLastStop) const {
   int r0, r1;
-  getRange(r0, r1);
+  getRange(r0, r1, ignoreLastStop);
   return r1;
 }
 

toonz/sources/toonzlib/txsheet.cpp

@@ -241,7 +241,49 @@ const TXshCell &TXsheet::getCell(const CellPosition &pos) const {
   if (!column) return emptyCell;
   TXshCellColumn *xshColumn = column->getCellColumn();
   if (!xshColumn) return emptyCell;
-  return xshColumn->getCell(pos.frame());
+  int frame = pos.frame();
+  TXshCell cell = xshColumn->getCell(frame);
+  if (cell.isEmpty() && Preferences::instance()->isImplicitHoldEnabled()) {
+    int r0, r1;
+    xshColumn->getRange(r0, r1);
+    for (int r = std::min(r1, pos.frame()); r >= r0; r--) {
+      TXshCell tempCell = xshColumn->getCell(r);
+      if (tempCell.isEmpty()) continue;
+      if (tempCell.getSoundLevel() || tempCell.getSoundTextLevel())
+        return emptyCell;
+      if (tempCell.getFrameId().isStopFrame() && cell.isEmpty())
+        return emptyCell;
+      frame = r;
+      break;
+    }
+  }
+  return xshColumn->getCell(frame);
+}
+
+//-----------------------------------------------------------------------------
+
+bool TXsheet::isImplicitCell(int row, int col) const {
+  return isImplicitCell(CellPosition(row, col));
+}
+
+bool TXsheet::isImplicitCell(const CellPosition &pos) const {
+  if (!Preferences::instance()->isImplicitHoldEnabled()) return false;
+
+  TXshColumnP column = m_imp->m_columnSet.getColumn(pos.layer());
+  if (!column) return false;
+  TXshCellColumn *xshColumn = column->getCellColumn();
+  if (!xshColumn) return false;
+  TXshCell tempCell = xshColumn->getCell(pos.frame());
+  if (!tempCell.isEmpty()) return false;
+
+  int r0, r1;
+  xshColumn->getRange(r0, r1);
+  for (int r = std::min(r1, pos.frame()); r >= r0; r--) {
+    tempCell = xshColumn->getCell(r);
+    if (!tempCell.isEmpty()) return true;
+    if (tempCell.getFrameId().isStopFrame()) return false;
+  }
+  return false;
 }
 
 //-----------------------------------------------------------------------------
@@ -251,8 +293,7 @@ bool TXsheet::setCell(int row, int col, const TXshCell &cell) {
 
   bool wasColumnEmpty = isColumnEmpty(col);
   TXshCellColumn *cellColumn;
-
-  if (!cell.isEmpty()) {
+  if (!cell.isEmpty() && !isImplicitCell(row, col)) {
     TXshLevel *level = cell.m_level.getPointer();
     assert(level);
 
@@ -297,7 +338,7 @@ bool TXsheet::setCell(int row, int col, const TXshCell &cell) {
   if (cell.isEmpty())
     updateFrameCount();
   else if (row >= m_imp->m_frameCount)
-    m_imp->m_frameCount = row + 1;
+    m_imp->m_frameCount = row + (cell.getFrameId().isStopFrame() ? 0 : 1);
 
   TNotifier::instance()->notify(TXsheetChange());
 
@@ -360,7 +401,7 @@ bool TXsheet::setCells(int row, int col, int rowCount, const TXshCell cells[]) {
   TXshCellColumn *column = touchColumn(col, type)->getCellColumn();
   if (!column) return false;
 
-  int oldColRowCount = column->getMaxFrame() + 1;
+  int oldColRowCount = column->getMaxFrame(true) + 1;
   bool ret           = column->setCells(row, rowCount, cells);
   if (!ret || column->isLocked()) {
     if (wasColumnEmpty) {
@@ -369,7 +410,7 @@ bool TXsheet::setCells(int row, int col, int rowCount, const TXshCell cells[]) {
     }
     return false;
   }
-  int newColRowCount = column->getMaxFrame() + 1;
+  int newColRowCount = column->getMaxFrame(true) + 1;
 
   TFx *fx = column->getFx();
   if (wasColumnEmpty && fx && fx->getOutputConnectionCount() == 0)
@@ -396,7 +437,7 @@ void TXsheet::insertCells(int row, int col, int rowCount) {
   if (!xshColumn) return;
   xshColumn->insertEmptyCells(row, rowCount);
   // aggiorno il frame count
-  int fc = xshColumn->getMaxFrame() + 1;
+  int fc = xshColumn->getMaxFrame(true) + 1;
   if (fc > m_imp->m_frameCount) m_imp->m_frameCount = fc;
 }
 
@@ -409,7 +450,7 @@ void TXsheet::removeCells(int row, int col, int rowCount) {
   TXshCellColumn *xshCellColumn = column->getCellColumn();
   if (!xshCellColumn) return;
 
-  int oldColRowCount = xshCellColumn->getMaxFrame() + 1;
+  int oldColRowCount = xshCellColumn->getMaxFrame(true) + 1;
   xshCellColumn->removeCells(row, rowCount);
 
   // aggiornamento framecount
@@ -427,7 +468,7 @@ void TXsheet::clearCells(int row, int col, int rowCount) {
   TXshCellColumn *xshCellColumn = column->getCellColumn();
   if (!xshCellColumn) return;
 
-  int oldColRowCount = xshCellColumn->getMaxFrame() + 1;
+  int oldColRowCount = xshCellColumn->getMaxFrame(true) + 1;
   xshCellColumn->clearCells(row, rowCount);
 
   // aggiornamento framecount
@@ -636,8 +677,12 @@ void TXsheet::reverseCells(int r0, int c0, int r1, int c1) {
   for (int j = c0; j <= c1; j++) {
     int i1, i2;
     for (i1 = r0, i2 = r1; i1 < i2; i1++, i2--) {
-      TXshCell app1 = getCell(CellPosition(i1, j));
-      TXshCell app2 = getCell(CellPosition(i2, j));
+      TXshCell app1;
+      if (!isImplicitCell(CellPosition(i1, j)))
+        app1 = getCell(CellPosition(i1, j));
+      TXshCell app2;
+      if (!isImplicitCell(CellPosition(i2, j)))
+        app2 = getCell(CellPosition(i2, j));
       setCell(i1, j, app2);
       setCell(i2, j, app1);
     }
@@ -654,7 +699,9 @@ void TXsheet::swingCells(int r0, int c0, int r1, int c1) {
 
   for (int j = c0; j <= c1; j++) {
     for (int i1 = r0Mod, i2 = r1 - 1; i2 >= r0; i1++, i2--) {
-      TXshCell cell = getCell(CellPosition(i2, j));
+      TXshCell cell;
+      if (!isImplicitCell(CellPosition(i2, j)))
+        cell = getCell(CellPosition(i2, j));
       setCell(i1, j, cell);
     }
   }
@@ -684,14 +731,17 @@ bool TXsheet::incrementCells(int r0, int c0, int r1, int c1,
       if (getCell(CellPosition(i + 1, j)).isEmpty()) continue;
 
       int frame1 = getCell(CellPosition(i, j)).getFrameId().getNumber();
-      if (frame1 == -1) break;
+      if (frame1 == TFrameId::EMPTY_FRAME || frame1 == TFrameId::STOP_FRAME)
+        break;
       while (!getCell(CellPosition(i + 1, j)).isEmpty() &&
+             !getCell(CellPosition(i + 1, j)).getFrameId().isStopFrame() &&
              getCell(CellPosition(i + 1, j)).getFrameId().getNumber() ==
                  getCell(CellPosition(i, j)).getFrameId().getNumber())
         i++, count++;
 
       int frame2 = getCell(CellPosition(i + 1, j)).getFrameId().getNumber();
-      if (frame2 == -1) break;
+      if (frame2 == TFrameId::EMPTY_FRAME || frame2 == TFrameId::STOP_FRAME)
+        break;
 
       if (frame1 + count == frame2)
         continue;
@@ -699,19 +749,26 @@ bool TXsheet::incrementCells(int r0, int c0, int r1, int c1,
       {
         int numCells = frame2 - frame1 - count;
         insertCells(i + 1, j, numCells);
+        TXshCell cell(0, TFrameId::NO_FRAME);
         forUndo.push_back(std::pair<TRect, TXshCell>(
-            TRect(i + 1, j, i + 1 + numCells - 1, j), TXshCell()));
-        for (int k = 1; k <= numCells; k++)
-          setCell(i + k, j, getCell(CellPosition(i, j)));
+            TRect(i + 1, j, i + 1 + numCells - 1, j), cell));
+        for (int k = 1; k <= numCells; k++) {
+          TXshCell cell;
+          if (!isImplicitCell(CellPosition(i + k, j)))
+            cell = getCell(CellPosition(i, j));
+          setCell(i + k, j, cell);
+        }
         i += numCells;
         r1 += numCells;
       } else  // remove
       {
         int numCells = count - frame2 + frame1;
         i            = i - numCells;
-        forUndo.push_back(
-            std::pair<TRect, TXshCell>(TRect(i + 1, j, i + 1 + numCells - 1, j),
-                                       getCell(CellPosition(i + 1, j))));
+        TXshCell cell;
+        if (!isImplicitCell(CellPosition(i + 1, j)))
+          cell = getCell(CellPosition(i + 1, j));
+        forUndo.push_back(std::pair<TRect, TXshCell>(
+            TRect(i + 1, j, i + 1 + numCells - 1, j), cell));
         removeCells(i + 1, j, numCells);
         r1 -= numCells;
       }
@@ -728,8 +785,13 @@ void TXsheet::duplicateCells(int r0, int c0, int r1, int c1, int upTo) {
 
   for (int j = c0; j <= c1; j++) {
     insertCells(r1 + 1, j, upTo - (r1 + 1) + 1);
-    for (int i = r1 + 1; i <= upTo; i++)
-      setCell(i, j, getCell(CellPosition(r0 + ((i - (r1 + 1)) % chunk), j)));
+    for (int i = r1 + 1; i <= upTo; i++) {
+      int row = r0 + ((i - (r1 + 1)) % chunk);
+      TXshCell cell;
+      if (!isImplicitCell(CellPosition(row, j)))
+        cell = getCell(CellPosition(row, j));
+      setCell(i, j, cell);
+    }
   }
 }
 
@@ -746,18 +808,20 @@ void TXsheet::stepCells(int r0, int c0, int r1, int c1, int type) {
   int k = 0;
   for (int r = r0; r <= r1; r++)
     for (int c = c0; c <= c1; c++) {
-      cells[k++] = getCell(CellPosition(r, c));
+      const TXshCell &cell = getCell(CellPosition(r, c));
+      cells[k++] = isImplicitCell(CellPosition(r, c)) ? TXshCell() : cell;
     }
 
   int nrows = nr * (type - 1);
 
   for (int c = c0; c <= c1; ++c) insertCells(r1 + 1, c, nrows);
 
+  bool useImplicitHold = Preferences::instance()->isImplicitHoldEnabled();
   for (int j = c0; j <= c1; j++) {
     int i, k;
     for (i = r0, k = j - c0; k < size; k += nc) {
       for (int i1 = 0; i1 < type; i1++) {
-        if (cells[k].isEmpty())
+        if (cells[k].isEmpty() || (useImplicitHold && i1 > 0))
           clearCells(i + i1, j);
         else
           setCell(i + i1, j, cells[k]);
@@ -772,13 +836,18 @@ void TXsheet::stepCells(int r0, int c0, int r1, int c1, int type) {
 void TXsheet::increaseStepCells(int r0, int c0, int &r1, int c1) {
   int c, size = r1 - r0 + 1;
   QList<int> ends;
+  bool useImplicit = Preferences::instance()->isImplicitHoldEnabled();
   for (c = c0; c <= c1; c++) {
     int r = r0, i = 0, rEnd = r1;
     while (r <= rEnd) {
       TXshCell cell = getCell(CellPosition(r, c));
       if (!cell.isEmpty()) {
-        insertCells(r, c);
-        setCell(r, c, cell);
+        if (useImplicit)
+          insertCells(r + 1, c);
+        else {
+          insertCells(r, c);
+          setCell(r, c, cell);
+        }
         rEnd++;
         r++;
         while (cell == getCell(CellPosition(r, c)) && r <= rEnd) r++;
@@ -848,7 +917,10 @@ void TXsheet::eachCells(int r0, int c0, int r1, int c1, int type) {
   for (j = r0, i = 0; i < size;
        j += type)  // in cells copio il contenuto delle celle che mi interessano
   {
-    for (k = c0; k <= c1; k++, i++) cells[i] = getCell(CellPosition(j, k));
+    for (k = c0; k <= c1; k++, i++) {
+      const TXshCell &cell = getCell(CellPosition(j, k));
+      cells[i] = isImplicitCell(j, k) ? TXshCell() : cell;
+    }
   }
 
   int c;
@@ -880,19 +952,29 @@ int TXsheet::reframeCells(int r0, int r1, int col, int type, int withBlank) {
   cells.clear();
 
   for (int r = r0; r <= r1; r++) {
-    if (cells.size() == 0 || cells.last() != getCell(CellPosition(r, col)))
-      cells.push_back(getCell(CellPosition(r, col)));
+    const TXshCell &cell = getCell(CellPosition(r, col));
+    if (cells.size() == 0 || cells.last() != cell) {
+      if (cell.isEmpty() && cells.last().getFrameId() == TFrameId::STOP_FRAME)
+        continue;
+      cells.push_back(cell);
+    }
   }
 
   // if withBlank is greater than -1, remove empty cells from cell order
   if (withBlank >= 0) {
     auto itr = cells.begin();
     while (itr != cells.end()) {
-      if ((*itr).isEmpty())
+      if ((*itr).isEmpty() || (*itr).getFrameId().isStopFrame())
         itr = cells.erase(itr);
       else
         itr++;
     }
+
+    // Convert implicit cell at end of selected range into a populated cell
+    if (withBlank > 0 && isImplicitCell((r1 + 1), col)) {
+      const TXshCell &origCell = getCell((r1 + 1), col);
+      setCell((r1 + 1), col, origCell);
+    }
   }
 
   if (cells.empty()) return 0;
@@ -913,9 +995,13 @@ int TXsheet::reframeCells(int r0, int r1, int col, int type, int withBlank) {
     removeCells(r0 + nrows, col, nr - nrows);
   }
 
+  bool useImplicitHold = Preferences::instance()->isImplicitHoldEnabled();
   for (int i = r0, k = 0; i < r0 + nrows; k++) {
+    TXshLevelP level = cells[k].m_level;
+    if (useImplicitHold && !level) level = getCell(i, col).m_level;
     for (int i1 = 0; i1 < type; i1++) {
-      if (cells[k].isEmpty())
+      // Cell is empty, find last level
+      if (cells[k].isEmpty() || (useImplicitHold && i1 > 0))
         clearCells(i + i1, col);
       else
         setCell(i + i1, col, cells[k]);
@@ -924,7 +1010,10 @@ int TXsheet::reframeCells(int r0, int r1, int col, int type, int withBlank) {
 
     if (withBlank > 0) {
       for (int i1 = 0; i1 < withBlank * type; i1++) {
-        clearCells(i + i1, col);
+        if (useImplicitHold && i1 == 0)
+          setCell(i + i1, col, TXshCell(level, TFrameId::STOP_FRAME));
+        else
+          clearCells(i + i1, col);
       }
       i += withBlank * type;
     }
@@ -1008,6 +1097,7 @@ void TXsheet::rolldownCells(int r0, int c0, int r1, int c1) {
                 If nr>r1-r0+1 add cells, otherwise remove cells. */
 void TXsheet::timeStretch(int r0, int c0, int r1, int c1, int nr) {
   int oldNr = r1 - r0 + 1;
+  bool useImplicitHold = Preferences::instance()->isImplicitHoldEnabled();
   if (nr > oldNr) /* ingrandisce */
   {
     int c;
@@ -1019,9 +1109,14 @@ void TXsheet::timeStretch(int r0, int c0, int r1, int c1, int nr) {
       getCells(r0, c, oldNr, cells.get());
       insertCells(r0 + 1, c, dn);
       int i;
-      for (i = nr - 1; i >= 0; i--) {
+      for (i = 0; i < nr; i++) {
         int j = i * double(oldNr) / double(nr);
-        if (j < i) setCell(i + r0, c, cells[j]);
+        if (j < i) {
+          int prevj = (i - 1) * double(oldNr) / double(nr);
+          TXshCell cell =
+              (useImplicitHold && j == prevj) ? TXshCell() : cells[j];
+          setCell(i + r0, c, cell);
+        }
       }
     }
   } else /* rimpicciolisce */
@@ -1035,7 +1130,12 @@ void TXsheet::timeStretch(int r0, int c0, int r1, int c1, int nr) {
       int i;
       for (i = 0; i < nr; i++) {
         int j = i * double(oldNr) / double(nr);
-        if (j > i) setCell(i + r0, c, cells[j]);
+        if (j > i) {
+          int prevj = (i - 1) * double(oldNr) / double(nr);
+          TXshCell cell =
+              (useImplicitHold && j == prevj) ? TXshCell() : cells[j];
+          setCell(i + r0, c, cell);
+        }
       }
       removeCells(r1 - dn + 1, c, dn);
     }
@@ -1170,9 +1270,12 @@ void TXsheet::updateFrameCount() {
   m_imp->m_frameCount = 0;
   for (int i = 0; i < m_imp->m_columnSet.getColumnCount(); ++i) {
     TXshColumnP cc = m_imp->m_columnSet.getColumn(i);
-    if (cc && !cc->isEmpty())
-      m_imp->m_frameCount =
-          std::max(m_imp->m_frameCount, cc->getMaxFrame() + 1);
+    if (cc && !cc->isEmpty()) {
+      int maxFrame  = cc->getMaxFrame();
+      TXshCell cell = getCell(maxFrame, i);
+      if (cell.getFrameId().isStopFrame()) maxFrame--;
+      m_imp->m_frameCount = std::max(m_imp->m_frameCount, maxFrame + 1);
+    }
   }
 }
 
@@ -1744,13 +1847,22 @@ void TXsheet::autoInputCellNumbers(int increment, int interval, int step,
   int rowUpTo = (r1 == -1) ? rowsCount - 1
                            : ((isOverwrite) ? std::min(r1, r0 + rowsCount - 1)
                                             : r0 + rowsCount - 1);
+  bool useImplicitHold = Preferences::instance()->isImplicitHoldEnabled();
+
   // for each column
   for (int c = 0; c < columnIndices.size(); c++) {
     int columnIndex  = columnIndices.at(c);
     TXshLevelP level = levels.at(c);
 
     // on insertion, insert empty cells first
-    if (!isOverwrite) insertCells(r0, columnIndex, rowsCount);
+    if (!isOverwrite) {
+      // If implicit cell, convert to real cell
+      if (isImplicitCell(r0, columnIndex)) {
+        TXshCell cell = getCell(r0, columnIndex);
+        setCell(r0, columnIndex, cell);
+      }
+      insertCells(r0, columnIndex, rowsCount);
+    }
 
     // obtain fids to be input
     std::vector<TFrameId> fids;
@@ -1794,11 +1906,19 @@ void TXsheet::autoInputCellNumbers(int increment, int interval, int step,
     int step_interv_itr = 0;
     while (row <= rowUpTo) {
       // input cell
-      if (step_interv_itr < step)
-        setCell(row, columnIndex, TXshCell(level, fids.at(fid_itr)));
+      if (step_interv_itr < step) {
+        TXshCell cell;
+        if (useImplicitHold && step_interv_itr == 0)
+          cell = TXshCell(level, fids.at(fid_itr));
+        setCell(row, columnIndex, cell);
+      }
       // .. or set empty cell as interval
-      else
-        setCell(row, columnIndex, TXshCell());
+      else {
+        TXshCell emptyCell;
+        if (useImplicitHold && step_interv_itr == step)
+          emptyCell = TXshCell(level, TFrameId::STOP_FRAME);
+        setCell(row, columnIndex, emptyCell);
+      }
 
       // increment
       step_interv_itr++;

toonz/sources/toonzlib/txshlevelcolumn.cpp

@@ -17,6 +17,8 @@ TFrameId qstringToFrameId(QString str) {
     return TFrameId::EMPTY_FRAME;
   else if (str == "-" || str == "-2")
     return TFrameId::NO_FRAME;
+  else if (str == "x" || str == "-3")
+    return TFrameId::STOP_FRAME;
 
   QString regExpStr = QString("^%1$").arg(TFilePath::fidRegExpStr());
   QRegExp rx(regExpStr);

toonz/sources/toonzlib/txshsoundcolumn.cpp

@@ -287,7 +287,7 @@ void TXshSoundColumn::saveData(TOStream &os) {
 
 //-----------------------------------------------------------------------------
 
-int TXshSoundColumn::getRange(int &r0, int &r1) const {
+int TXshSoundColumn::getRange(int &r0, int &r1, bool ignoreLastStop) const {
   r0 = getFirstRow();
   r1 = getMaxFrame();
   return r1 - r0 + 1;
@@ -301,7 +301,7 @@ int TXshSoundColumn::getRowCount() const {
 
 //-----------------------------------------------------------------------------
 
-int TXshSoundColumn::getMaxFrame() const {
+int TXshSoundColumn::getMaxFrame(bool ignoreLastStop) const {
   int levelsCount = m_levels.size();
   if (levelsCount == 0) return -1;
   return m_levels.at(levelsCount - 1)->getVisibleEndFrame();

toonz/sources/toonzlib/txshzeraryfxcolumn.cpp

@@ -7,6 +7,7 @@
 #include "toonz/txsheet.h"
 #include "toonz/fxdag.h"
 #include "toonz/txshzeraryfxlevel.h"
+#include "toonz/preferences.h"
 
 #include "tstream.h"
 
@@ -21,6 +22,7 @@ TXshZeraryFxColumn::TXshZeraryFxColumn(int frameCount)
   m_zeraryColumnFx->setColumn(this);
   m_zeraryFxLevel->addRef();
   m_zeraryFxLevel->setColumn(this);
+  if (frameCount <= 0) return;
   for (int i = 0; i < frameCount; i++)
     setCell(i, TXshCell(m_zeraryFxLevel, TFrameId(1)));
 }
@@ -37,8 +39,13 @@ TXshZeraryFxColumn::TXshZeraryFxColumn(const TXshZeraryFxColumn &src)
   m_zeraryFxLevel->setColumn(this);
   m_first = src.m_first;
   int i;
-  for (i = 0; i < (int)src.m_cells.size(); i++)
-    m_cells.push_back(TXshCell(m_zeraryFxLevel, src.m_cells[i].getFrameId()));
+  for (i = 0; i < (int)src.m_cells.size(); i++) {
+    if (Preferences::instance()->isImplicitHoldEnabled() &&
+        src.m_cells[i].getFrameId().isEmptyFrame())
+      m_cells.push_back(TXshCell(0, src.m_cells[i].getFrameId()));
+    else
+      m_cells.push_back(TXshCell(m_zeraryFxLevel, src.m_cells[i].getFrameId()));
+  }
   assert((int)src.m_cells.size() == (int)m_cells.size());
   TFx *fx = src.getZeraryColumnFx()->getZeraryFx();
   if (fx) {
@@ -104,9 +111,13 @@ bool TXshZeraryFxColumn::setCells(int row, int rowCount,
   bool isEmptyColumn = isEmpty() && getZeraryColumnFx()->getZeraryFx() == 0;
   int i;
   for (i = 0; i < rowCount; i++) {
-    if (isEmptyColumn)
-      newCells.push_back(TXshCell(m_zeraryFxLevel, cells[i].getFrameId()));
-    else
+    if (isEmptyColumn) {
+      if (Preferences::instance()->isImplicitHoldEnabled() &&
+          cells[i].getFrameId().isEmptyFrame())
+        newCells.push_back(TXshCell(0, cells[i].getFrameId()));
+      else
+        newCells.push_back(TXshCell(m_zeraryFxLevel, cells[i].getFrameId()));
+    } else
       newCells.push_back(cells[i]);
   }
   // Sto settando delle celle in una colonna nuova, devo settare anche
@@ -141,7 +152,7 @@ void TXshZeraryFxColumn::loadData(TIStream &is) {
 
   int r0, r1;
   bool touched = false;
-  const TXshCell cell(m_zeraryFxLevel, TFrameId(1));
+  TXshCell cell(m_zeraryFxLevel, TFrameId(1));
   std::string tagName;
   while (is.matchTag(tagName)) {
     if (tagName == "status") {
@@ -157,6 +168,10 @@ void TXshZeraryFxColumn::loadData(TIStream &is) {
           }
           int r, n;
           is >> r >> n;
+          if (is.getTagAttribute("stopframe") == "yes")
+            cell.m_frameId = TFrameId::STOP_FRAME;
+          else
+            cell.m_frameId = 1;
           for (int i = 0; i < n; i++) setCell(r++, cell);
         } else
           throw TException("expected <cell>");
@@ -181,9 +196,35 @@ void TXshZeraryFxColumn::saveData(TOStream &os) {
     for (int r = r0; r <= r1; r++) {
       TXshCell cell = getCell(r);
       if (cell.isEmpty()) continue;
-      int n = 1;
-      while (r + n <= r1 && !getCell(r + n).isEmpty()) n++;
-      os.child("cell") << r << n;
+      int fnum           = cell.m_frameId.getNumber();
+      if (fnum > 1) fnum = 1;  // Should always be 1 unless it's stopframe
+      int n              = 1;
+
+      if (r < r1) {
+        TXshCell cell2 = getCell(r + 1);
+        if (!cell2.isEmpty()) {
+          int fnum2            = cell2.m_frameId.getNumber();
+          if (fnum2 > 1) fnum2 = 1;  // Should always be 1 unless it's stopframe
+          if (fnum == fnum2) {
+            n++;
+            for (;;) {
+              if (r + n > r1) break;
+              cell2 = getCell(r + n);
+              if (cell2.isEmpty()) break;
+              fnum2 = cell2.m_frameId.getNumber();
+              if (fnum2 > 1)
+                fnum2 = 1;  // Should always be 1 unless it's stopframe
+              if (fnum != fnum2) break;
+              n++;
+            }
+          }
+        }
+      }
+      std::map<std::string, std::string> attr;
+      if (cell.m_frameId.isStopFrame()) attr["stopframe"] = "yes";
+      os.openChild("cell", attr);
+      os << r << n;
+      os.closeChild();
       r += n - 1;
     }
     os.closeChild();